Difference between revisions of "Network configuration"

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(Undo revision 451390 by T.ask (talk) - the note makes sense only *after* showing what the permanent IP substitutes)
 
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[[Category:Networking]]
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[[Category:Network configuration]]
[[Category:Getting and installing Arch]]
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[[cs:Network configuration]]
[[cs:Configuring Network]]
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[[el:Network configuration]]
[[es:Configuring Network]]
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[[es:Network configuration]]
 
[[fr:Connexions reseau]]
 
[[fr:Connexions reseau]]
[[it:Configuring Network]]
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[[it:Network configuration]]
[[ja:Network Configuration]]
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[[ja:ネットワーク設定]]
[[nl:Configuring Network]]
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[[nl:Network configuration]]
[[pt:Configuring Network]]
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[[pt:Network configuration]]
 
[[ro:Configurare retea]]
 
[[ro:Configurare retea]]
[[ru:Configuring Network]]
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[[ru:Network configuration]]
[[sk:Configuring Network]]
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[[sk:Network configuration]]
[[tr:Ağ_Yapılandırması]]
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[[tr:Ağ Yapılandırması]]
[[zh-CN:Configuring Network]]
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[[zh-cn:Network configuration]]
{{Article summary start}}
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[[zh-tw:Network configuration]]
{{Article summary text|A simple guide for setting up and troubleshooting network.}}
+
{{Related articles start}}
{{Article summary heading|Overview}}
+
{{Related|Jumbo frames}}
{{Article summary text|{{Networking overview}}}}
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{{Related|Firewalls}}
{{Article summary heading|Related}}
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{{Related|Wireless network configuration}}
{{Article summary wiki|Jumbo Frames}}
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{{Related|Network bridge}}
{{Article summary wiki|Firewalls}}
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{{Related|List of applications/Internet#Network managers}}
{{Article summary wiki|Samba}}
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{{Related articles end}}
{{Article summary wiki|Wireless Setup}}
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{{Article summary end}}
+
  
This page explains how to set up a '''wired''' connection to a network. If you need to set up '''wireless''' networking see the [[Wireless_Setup|Wireless Setup]] page.
+
This page explains how to set up a '''wired''' connection to a network. If you need to set up '''wireless''' networking see the [[Wireless network configuration]] page.
  
 
== Check the connection ==
 
== Check the connection ==
{{Note|If you receive an error like {{ic|ping: icmp open socket: Operation not permitted}} when executing ping, try to re-install the {{ic|iputils}} package.}} 
 
  
Many times, the basic installation procedure has created a working network configuration. To check if this is so, use the following command:
+
The basic installation procedure typically has a functional network configuration. Use {{man|8|ping}} to check the connection:
  
{{Note|The {{ic|-c 3}} option calls it three times. See {{ic|man ping}} for more information.}}
+
{{hc|$ ping www.google.com|2=
 +
PING www.l.google.com (74.125.132.105) 56(84) bytes of data.
 +
64 bytes from wb-in-f105.1e100.net (74.125.132.105): icmp_req=1 ttl=50 time=17.0 ms
 +
...
 +
}}
  
{{hc|$ ping -c 3 www.google.com|2=
+
If the ping is successful (you see 64 bytes messages as above), then the network is configured. Press {{ic|Control-C}} to stop the ping.
PING www.l.google.com (74.125.224.146) 56(84) bytes of data.
+
64 bytes from 74.125.224.146: icmp_req=1 ttl=50 time=437 ms
+
64 bytes from 74.125.224.146: icmp_req=2 ttl=50 time=385 ms
+
64 bytes from 74.125.224.146: icmp_req=3 ttl=50 time=298 ms
+
  
--- www.l.google.com ping statistics ---
+
If the ping failed with an ''Unknown hosts'' error, it  means that your machine was unable to resolve this domain name. It may be related to your service provider or your router/gateway. Try pinging a static IP address to prove that your machine has access to the Internet:
3 packets transmitted, 3 received, 0% packet loss, time 1999ms
+
rtt min/avg/max/mdev = 298.107/373.642/437.202/57.415 ms}}
+
  
If it works, then you may only wish to personalize your settings from the options below.
+
{{hc|$ ping 8.8.8.8|<nowiki>
 
+
If the previous command complains about unknown hosts, it means that your machine was unable to resolve this domain name. It might be related to your service provider or your router/gateway. You can try pinging a static IP address to prove that your machine has access to the Internet.
+
 
+
{{hc|$ ping -c 3 8.8.8.8|2=
+
 
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
 
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
 
64 bytes from 8.8.8.8: icmp_req=1 ttl=53 time=52.9 ms
 
64 bytes from 8.8.8.8: icmp_req=1 ttl=53 time=52.9 ms
64 bytes from 8.8.8.8: icmp_req=2 ttl=53 time=72.5 ms
+
...
64 bytes from 8.8.8.8: icmp_req=3 ttl=53 time=70.6 ms
+
</nowiki>}}
  
--- 8.8.8.8 ping statistics ---
+
If you are able to ping {{ic|8.8.8.8}} but not {{ic|www.google.com}}, check your DNS configuration. See [[resolv.conf]] for details. The {{ic|hosts}} line in {{ic|/etc/nsswitch.conf}} is another place you can check.
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
+
rtt min/avg/max/mdev = 52.975/65.375/72.543/8.803 ms}}
+
  
{{Note|{{ic|8.8.8.8}} is a static address that is easy to remember. It is the address of Google's primary DNS server, therefore it can be considered reliable, and is generally not blocked by content filtering systems and proxies.}}
+
If not, check for cable issues before diagnosing further.
  
If you are able to ping this address, you may try adding this nameserver to your {{ic|/etc/resolv.conf}} file.
+
{{Note|
 +
* If you receive an error like {{ic|ping: icmp open socket: Operation not permitted}} when executing ''ping'', try to re-install the {{Pkg|iputils}} package.
 +
* The {{ic|-c ''num''}} option can be used to make exactly {{ic|''num''}} pings, otherwise it pings infinitely and has to be terminated manually. See {{ic|man ping}} for more information.
 +
* {{ic|8.8.8.8}} is a static address that is easy to remember. It is the address of Google's primary DNS server, therefore it can be considered reliable, and is generally not blocked by content filtering systems and proxies.
 +
}}
  
 
== Set the hostname ==
 
== Set the hostname ==
  
A [[Wikipedia:Hostname|hostname]] is a unique name created to identify a machine on a network: it is configured in {{ic|/etc/hostname}}. The file can contain the system's domain name, if any. To set the hostname, do:
+
A [[Wikipedia:Hostname|hostname]] is a unique name created to identify a machine on a network, configured in {{ic|/etc/hostname}}—see {{man|5|hostname}} and {{man|7|hostname}} for details. The file can contain the system's domain name, if any. To set the hostname, [[textedit|edit]] {{ic|/etc/hostname}} to include a single line with {{ic|''myhostname''}}:
  
# hostnamectl set-hostname '''myhostname'''
+
{{hc|/etc/hostname|
 +
''myhostname''
 +
}}
  
This will put '''myhostname''' in {{ic|/etc/hostname}}.
+
{{Tip|For advice on choosing a hostname, see [https://tools.ietf.org/html/rfc1178 RFC 1178].}}
  
See {{ic|man 5 hostname}} and {{ic|man 1 hostnamectl}} for details.
+
Alternatively, using {{man|1|hostnamectl}}:
  
{{Note|
+
# hostnamectl set-hostname ''myhostname''
*{{ic|hostnamectl}} supports FQDNs
+
*You no longer need to edit {{ic|/etc/hosts}}, {{pkg|systemd}} will provide host name resolution, and is installed on all systems by default.}}
+
  
To set the hostname temporarily (until a reboot), use the {{ic|hostname}} command from {{Pkg|inetutils}}:
+
To temporarily set the hostname (until reboot), use {{man|1|hostname}} from {{Pkg|inetutils}}:
  
 
  # hostname ''myhostname''
 
  # hostname ''myhostname''
  
== Device Driver ==
+
To set the "pretty" hostname and other machine metadata, see {{man|5|machine-info|https://www.freedesktop.org/software/systemd/man/machine-info.html}}.
  
=== Check the driver status ===
+
=== Local network hostname resolution ===
  
Udev should detect your network interface card ([[Wikipedia:Network_interface_controller|NIC]]) and automatically load the necessary module at start up. Check the "Ethernet controller" entry (or similar) from the {{ic|lspci -v}} output. It should tell you which kernel module contains the driver for your network device. For example:
+
The pre-requisite is to [[#Set the hostname]], after which hostname resolution works on the local system itself:
 +
 
 +
{{hc|$ ping ''myhostname''|2=
 +
PING myhostname (192.168.1.2) 56(84) bytes of data.
 +
64 bytes from myhostname (192.168.1.2): icmp_seq=1 ttl=64 time=0.043 ms}}
 +
 
 +
To allow other machines to address the host by name, it is necessary to either:
 +
 
 +
* Configure the {{man|5|hosts}} file, or
 +
* Enable a service which resolves the hostname.
 +
 
 +
{{Note|1={{Pkg|systemd}} provides hostname resolution via the {{ic|myhostname}} nss module, enabled by default in {{ic|/etc/nsswitch.conf}}. However, clients may still rely on {{ic|/etc/hosts}}, see [https://lists.debian.org/debian-devel/2013/07/msg00809.html] [https://bugzilla.mozilla.org/show_bug.cgi?id=87717#c55] for examples.}}
 +
 
 +
To configure the hosts file, add the following line to {{ic|/etc/hosts}}:
 +
 
 +
127.0.1.1 ''myhostname''.localdomain ''myhostname''
 +
 
 +
As a result the system resolves to both entries:
 +
 
 +
$ getent hosts
 +
127.0.0.1      localhost
 +
127.0.1.1      myhostname.localdomain myhostname
 +
 
 +
For a system with a permanent IP address, that permanent IP address should be used instead of {{ic|127.0.1.1}}.
 +
 
 +
{{Note|1=Another option is to set up a full DNS server such as [[BIND]] or [[Unbound]], but that is overkill and too complex for most systems. For small networks and dynamic flexibility with hosts joining and leaving the network [[Wikipedia:Zero-configuration_networking|zero-configuration networking]] services may be more applicable:
 +
*[[Samba]] provides hostname resolution via Microsoft's '''NetBIOS'''. It only requires installation of {{Pkg|samba}} and enabling of the {{ic|nmbd.service}} service. Computers running Windows, macOS, or Linux with {{ic|nmbd}} running, will be able to find your machine.
 +
*[[Avahi]] provides hostname resolution via '''zeroconf''', also known as Avahi or Bonjour. It requires slightly more complex configuration than Samba: see [[Avahi#Hostname resolution]] for details. Computers running macOS, or Linux with an Avahi daemon running, will be able to find your machine. Windows does not have an built-in Avahi client or daemon.
 +
}}
 +
 
 +
== Device driver ==
 +
 
 +
=== Check the status ===
 +
 
 +
[[udev]] should detect your network interface card (see [[Wikipedia:Network interface controller]]) and automatically load the necessary module at start up. Check the "Ethernet controller" entry (or similar) from the {{ic|lspci -v}} output. It should tell you which kernel module contains the driver for your network device. For example:
  
 
{{hc|$ lspci -v|
 
{{hc|$ lspci -v|
02:00.0 Ethernet controller: Attansic Technology Corp. L1 Gigabit Ethernet Adapter (rev b0)
+
02:00.0 Ethernet controller: Attansic Technology Corp. L1 Gigabit Ethernet Adapter (rev b0)
 
  ...
 
  ...
 
  Kernel driver in use: atl1
 
  Kernel driver in use: atl1
  Kernel modules: atl1}}
+
  Kernel modules: atl1
 +
}}
  
 
Next, check that the driver was loaded via {{ic|dmesg <nowiki>|</nowiki> grep ''module_name''}}. For example:
 
Next, check that the driver was loaded via {{ic|dmesg <nowiki>|</nowiki> grep ''module_name''}}. For example:
  
 
  $ dmesg | grep atl1
 
  $ dmesg | grep atl1
    ...
+
    ...
    atl1 0000:02:00.0: eth0 link is up 100 Mbps full duplex
+
    atl1 0000:02:00.0: eth0 link is up 100 Mbps full duplex
  
 
Skip the next section if the driver was loaded successfully. Otherwise, you will need to know which module is needed for your particular model.
 
Skip the next section if the driver was loaded successfully. Otherwise, you will need to know which module is needed for your particular model.
  
=== Load the device module ===
+
=== Load the module ===
  
Google for the right module/driver for the chipset. Once you know which module to use, you can [[Kernel modules#Loading|load it]] with:
+
Search in the Internet for the right module/driver for the chipset. Some common modules are {{ic|8139too}} for cards with a Realtek chipset, or {{ic|sis900}} for cards with a SiS chipset. Once you know which module to use, try to [[Kernel modules#Manual module handling|load it manually]]. If you get an error saying that the module was not found, it's possible that the driver is not included in Arch kernel. You may search the [[AUR]] for the module name.
  
# modprobe ''module_name''
+
If udev is not detecting and loading the proper module automatically during bootup, see [[Kernel modules#Automatic module handling]].
  
If udev is not detecting and loading the proper module automatically during bootup, you can add it to a {{ic|*.conf}} file from the {{ic|/etc/modules-load.d/}} folder so that you do not need to {{ic|modprobe}} it every time you boot. For example, if {{ic|tg3}} is the network module:
+
== Network interfaces ==
  
# tee /etc/modules-load.d/tg3.conf <<< "tg3"
+
=== Device names ===
  
Other common modules are {{ic|8139too}} for cards with a Realtek chipset, or {{ic|sis900}} for cards with a SiS chipset.
+
For computers with multiple NICs, it is important to have fixed device names. Many configuration problems are caused by interface name changing.
  
== Network Interfaces ==
+
[[udev]] is responsible for which device gets which name. Systemd v197 introduced [http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames Predictable Network Interface Names], which automatically assigns static names to network devices. Interfaces are now prefixed with {{ic|en}} (wired/[[w:Ethernet|Ethernet]]), {{ic|wl}} (wireless/WLAN), or {{ic|ww}} ([[w:Wireless_WAN|WWAN]]) followed by an automatically generated identifier, creating an entry such as {{ic|enp0s25}}. This behavior may be disabled by adding {{ic|1=net.ifnames=0}} to the [[kernel parameters]].
  
=== Device names ===
+
{{Note|When changing the interface naming scheme, do not forget to update all network-related configuration files and custom systemd unit files to reflect the change. Specifically, if you have [[netctl#Basic method|netctl static profiles]] enabled, run {{ic|netctl reenable ''profile''}} to update the generated service file.}}
  
For motherboards that have integrated NICs, it is important to have fixed device name. Many configuration problems are caused by interface name changing.
+
==== Get current device names ====
  
[[Udev]] is responsible for which device gets which name. Systemd v197 introduced [http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames Predictable Network Interface Names], which automatically assigns static names to network devices. Interfaces are now prefixed with en (ethernet), wl (WLAN), or ww (WWAN) followed by an automatically generated identifier, creating an entry such as {{ic|enp0s25}}.  
+
Current NIC names can be found via {{ic|sysfs}} or {{ic|ip link}}. For example:
  
This behavior may be disabled by adding a symlink:
+
{{hc|$ ls /sys/class/net|
 +
lo enp0s3
 +
}}
  
# ln -s /dev/null /etc/udev/rules.d/80-net-name-slot.rules
+
{{hc|$ ip link|
 +
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default
 +
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
 +
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
 +
    link/ether 08:00:27:23:6f:3a brd ff:ff:ff:ff:ff:ff
 +
}}
  
Users upgrading from an earlier systemd version will have a blank rules file created automatically. So if you want to use persistent device names, just delete the file.
+
Wireless device names can also be retrieved using {{ic|iw dev}}. See [[Wireless network configuration#Getting some useful information]] for details.
  
 
==== Change device name ====
 
==== Change device name ====
You can change the device name by defining the name manually with an udev-rule. For example:
+
 
{{hc|/etc/udev/rules.d/10-network.rules|2=
+
You can change the device name by defining the name manually with an udev-rule. For example:
 +
 
 +
{{hc|/etc/udev/rules.d/10-network.rules|<nowiki>
 
SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="aa:bb:cc:dd:ee:ff", NAME="net1"
 
SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="aa:bb:cc:dd:ee:ff", NAME="net1"
SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="ff:ee:dd:cc:bb:aa", NAME="net0"}}
+
SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="ff:ee:dd:cc:bb:aa", NAME="net0"
A couple things to note:
+
</nowiki>}}
  
* To get the MAC address of each card, use this command: {{ic|cat /sys/class/net/'''device-name'''/address}}<!-- {{ic|<nowiki>udevadm info -a -p /sys/class/net/<yourdevice> | grep address | tr [A-Z] [a-z]</nowiki>}} -->
+
These rules will be applied automatically at boot.
* Make sure to use the lower-case hex values in your udev rules. It doesn't like upper-case.
+
{{Note|When choosing the static names '''it should be avoided to use names in the format of "eth''X''" and "wlan''X''"''', because this may lead to race conditions between the kernel and udev during boot. Instead, it is better to use interface names that are not used by the kernel as default, e.g.: {{ic|net0}}, {{ic|net1}}, {{ic|wifi0}}, {{ic|wifi1}}. For further details please see the [http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames systemd] documentation.}}
+
  
=== Get current device names ===
+
A couple of things to note:
  
Current NIC names can be found via sysfs
+
* To get the MAC address of each card, use this command: {{ic|cat /sys/class/net/''device_name''/address}}
 +
* Make sure to use the lower-case hex values in your udev rules. It doesn't like upper-case.
  
{{hc|$ ls /sys/class/net|
+
If the network card has a dynamic MAC, you can use {{ic|DEVPATH}}, for example:
lo eth0 eth1 firewire0}}
+
  
=== Enabling and disabling network interfaces ===
+
{{hc|/etc/udev/rules.d/10-network.rules|<nowiki>
 +
SUBSYSTEM=="net", DEVPATH=="/devices/platform/wemac.*", NAME="int"
 +
SUBSYSTEM=="net", DEVPATH=="/devices/pci*/*1c.0/*/net/*", NAME="en"
 +
</nowiki>}}
  
You can activate or deactivate network interfaces using:
+
The device path should match both the new and old device name, since the rule may be executed more than once on bootup. For example, in the second rule, {{ic|"/devices/pci*/*1c.0/*/net/enp*"}} would be wrong since it will stop matching once the name is changed to {{ic|en}}. Only the system-default rule will fire the second time around, causing the name to be changed back to e.g. {{ic|enp1s0}}.
  
# ip link set eth0 up
+
To [[Udev#Testing_rules_before_loading|test]] your rules, they can be triggered directly from userspace, e.g. with {{ic|udevadm --debug test /sys/''DEVPATH''}}. Remember to first take down the interface you are trying to rename (e.g. {{ic|ip link set enp1s0 down}}).
# ip link set eth0 down
+
  
To check the result:
+
{{Note|When choosing the static names '''it should be avoided to use names in the format of "eth''X''" and "wlan''X''"''', because this may lead to race conditions between the kernel and udev during boot. Instead, it is better to use interface names that are not used by the kernel as default, e.g.: {{ic|net0}}, {{ic|net1}}, {{ic|wifi0}}, {{ic|wifi1}}. For further details please see the [http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames systemd] documentation.}}
  
{{hc|$ ip link show dev eth0|
+
==== Reverting to traditional device names ====
2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master br0 state UP mode DEFAULT qlen 1000
+
[...]}}
+
  
== Configure the IP address ==
+
If you would prefer to retain traditional interface names such as eth0,  [http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames Predictable Network Interface Names] can be disabled with the following:
  
You have two options: a dynamically assigned address using [[Wikipedia:Dynamic Host Configuration Protocol|DHCP]], or an unchanging "static" address.
+
  # ln -s /dev/null /etc/udev/rules.d/80-net-setup-link.rules
+
=== Dynamic IP address ===
+
  
==== Manually run DHCP Client Daemon ====
+
=== Set device MTU and queue length ===
  
Please note that {{ic|dhcpcd}} is not {{ic|dhcpd}}.
+
You can change the device MTU and queue length by defining manually with an udev-rule. For example:
  
{{hc|# dhcpcd eth0|
+
{{hc|/etc/udev/rules.d/10-network.rules|<nowiki>
dhcpcd: version 5.1.1 starting
+
ACTION=="add", SUBSYSTEM=="net", KERNEL=="wl*", ATTR{mtu}="1480", ATTR{tx_queue_len}="2000"
dhcpcd: eth0: broadcasting for a lease
+
</nowiki>}}
...
+
dhcpcd: eth0: leased 192.168.1.70 for 86400 seconds}}
+
  
And now, {{ic|ip addr show dev eth0}} should show your inet address.
+
=== Enabling and disabling network interfaces ===
  
For some people, {{ic|dhclient}} (from the {{Pkg|dhclient}} package) works where {{ic|dhcpcd}} fails.
+
You can activate or deactivate network interfaces using:
  
==== Run DHCP at boot ====
+
# ip link set eth0 up
 +
# ip link set eth0 down
  
If you simply want to use DHCP for your Ethernet connection, you can use {{ic|dhcpcd@.service}} (provided by the {{Pkg|dhcpcd}} package).
+
To check the result:
  
To start DHCP for {{ic|eth0}}, simply use:
+
{{hc|$ ip link show dev eth0|
 +
2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master br0 state UP mode DEFAULT qlen 1000
 +
...
 +
}}
  
  # systemctl start dhcpcd@eth0
+
{{Note| If your default route is through interface {{ic|eth0}}, taking it down will also remove the route, and bringing it back up will not automatically reestablish the default route. See [[#Manual assignment]] for reestablishing it.}}
  
You can enable the service to automatically start at boot with:
+
== Configure the IP address ==
  
# systemctl enable dhcpcd@eth0
+
{{Warning|Use a single method to manage the network, as several methods may conflict.}}
  
If the dhcpd service starts before your network card module ({{bug|30235}}), manually add your network card to {{ic|/etc/modules-load.d/*.conf}}. For example, if your Realtek card needs {{ic|r8169}} to be loaded, create:
+
You have two options: a dynamically assigned address using [[Wikipedia:Dynamic Host Configuration Protocol|DHCP]], or an unchanging "static" address. See also [[List of applications#Network managers]].
  
{{hc|/etc/modules-load.d/realtek.conf|
+
=== Dynamic IP address ===
r8169}}
+
  
{{Tip|To find out which modules are used by your network card, use {{ic|lspci -k}}.}}
+
==== systemd-networkd ====
  
If you use DHCP and you do '''not''' want your DNS servers automatically assigned every time you start your network, be sure to add the following to the last section of {{ic|dhcpcd.conf}}:
+
An easy way to setup DHCP for simple requirements is to use [[systemd-networkd]] service provided by systemd. See [[systemd-networkd#Basic DHCP network]].  
  
{{hc|/etc/dhcpcd.conf|
+
==== dhcpcd ====
nohook resolv.conf}}
+
  
To prevent {{ic|dhcpcd}} from adding domain name servers to {{ic|/etc/resolv.conf}}, use the {{ic|nooption}} option:
+
[[dhcpcd]] is the default client in Arch Linux to setup DHCP on the installation ISO. It is a powerful tool with many configurable DHCP client options. See [[dhcpcd#Running]] on how to activate it for an interface.
  
{{hc|/etc/dhcpcd.conf|
+
==== dhclient ====
nooption domain_name_servers}}
+
  
Then add your own DNS name server to {{ic|/etc/resolv.conf}}.
+
{{Pkg|dhclient}} is the Internet Systems Consortium DHCP client. [[Enable]] the {{ic|dhclient@''interface''.service}}, where {{ic|''interface''}} is a wired [[#Device name]]. See {{man|8|dhclient|url=}} and {{man|5|dhclient.conf|url=}} for details.
  
You may use the {{Pkg|openresolv}} package if several different processes want to control {{ic|/etc/resolv.conf}} (e.g. {{Pkg|dhcpcd}} and a VPN client). No additional configuration for {{Pkg|dhcpcd}} is needed to use {{Pkg|openresolv}}.
+
==== netctl ====
 +
 
 +
[[netctl]] is a CLI-based tool for configuring and managing network connections through user-created profiles. Create a profile as shown in [[netctl#Example profiles]], then enable it as described in [[netctl#Basic method]].
  
 
=== Static IP address ===
 
=== Static IP address ===
  
There are various reasons why you may wish to assign static IP addresses on your network. For instance, one may gain a certain degree of predictability with unchanging addresses, or you may not have a DHCP server available.
+
A static IP address can be configured with most standard Arch Linux networking tools. Independent of the tool you choose, you will probably need to be prepared with the following information:
 
+
{{Note|If you share your Internet connection from a Windows machine without a router, be sure to use static IP addresses on both computers to avoid LAN problems.}}
+
 
+
You need:
+
  
 
* Static IP address
 
* Static IP address
* [[Wikipedia:Subnetwork|Subnet mask]]
+
* Subnet mask, or possibly its [[wikipedia:Classless Inter-Domain Routing#CIDR notation|CIDR notation]], for example {{ic|/24}} is the CIDR notation of {{ic|255.255.255.0}} netmask.
 
* [[Wikipedia:Broadcast_address|Broadcast address]]
 
* [[Wikipedia:Broadcast_address|Broadcast address]]
 
* [[Wikipedia:Default_gateway|Gateway]]'s IP address
 
* [[Wikipedia:Default_gateway|Gateway]]'s IP address
 +
* Name server (DNS) IP addresses. See also [[resolv.conf]].
  
If you are running a private network, it is safe to use IP addresses in 192.168.*.* for your IP addresses, with a subnet mask of 255.255.255.0 and a broadcast address of 192.168.*.255. The gateway is usually 192.168.*.1 or 192.168.*.254.
+
If you are running a private network, it is safe to use IP addresses in {{ic|192.168.*.*}} for your IP addresses, with a subnet mask of {{ic|255.255.255.0}} and a broadcast address of {{ic|192.168.*.255}}. The gateway is usually {{ic|192.168.*.1}} or {{ic|192.168.*.254}}.
  
==== Manual assignment ====
+
{{Warning|
 +
* Make sure manually assigned IP addresses do not conflict with DHCP assigned ones. See [http://www.raspberrypi.org/forums/viewtopic.php?f&#61;28&t&#61;16797 this forum thread].
 +
* If you share your Internet connection from a Windows machine without a router, be sure to use static IP addresses on both computers to avoid LAN problems.
 +
}}
  
You can assign a static IP address in the console:
+
{{Tip|Addresses can be calculated with the {{Pkg|ipcalc}} package; see [[#Calculating addresses]].}}
  
# ip addr add <IP address>/<subnet mask> dev <interface>
+
==== netctl ====
  
For example:
+
To create a [[netctl]] profile with a static IP, set the {{ic|1=IP=static}} option as well as {{ic|Address}}, {{ic|Gateway}}, and {{ic|DNS}}. See [[netctl#Wired]].
  
# ip addr add 192.168.1.2/24 dev eth0
+
==== systemd-networkd ====
  
{{Note|The subnet mask was specified using [[Wikipedia:CIDR_notation|CIDR notation]].}}
+
The [[systemd-networkd]] service provided by systemd can set up a static IP using a simple configuration file. See [[systemd-networkd#Wired adapter using a static IP]].
  
For more options, see {{ic|man ip}}.
+
==== dhcpcd ====
  
Add your gateway like so:
+
See [[dhcpcd#Static profile]].
  
# ip route add default via <default gateway IP address>
+
==== Manual assignment ====
  
For example:
+
It is possible to manually set up a static IP using only the {{pkg|iproute2}} package. This is a good way to test connection settings since the connection made using this method will not persist across reboots. First enable the [[#Network interfaces|network interface]]:
  
  # ip route add default via 192.168.1.1
+
  # ip link set ''interface'' up
  
If you the get the error "No such process", it means you have to run {{ic|ip link set dev eth0 up}} as root.
+
Assign a static IP address in the console:
  
====Manual connection at boot using systemd====
+
# ip addr add ''IP_address''/''subnet_mask'' broadcast ''broadcast_address'' dev ''interface''
This section details how to manually connect using [[systemd]].
+
  
{{Note|We use {{ic|net0}} as the interface name in these examples, you have to replace all occurrences (including those in the {{ic|BindsTo}} and {{ic|After}} values) with the name of the interface you are configuring.}}
+
Then add your gateway IP address:
  
=====Using [[dhcpcd]]=====
+
# ip route add default via ''default_gateway''
Create the file {{ic|/etc/systemd/system/network.service}} using your editor of choice. This example uses [[wpa_supplicant]].
+
{{hc|/etc/systemd/system/network.service|<nowiki>
+
[Unit]
+
Description=Network Connectivity
+
Wants=network.target
+
Before=network.target
+
BindsTo=sys-subsystem-net-devices-net0.device
+
After=sys-subsystem-net-devices-net0.device
+
  
[Service]
+
For example:
Type=oneshot
+
RemainAfterExit=yes
+
ExecStart=/usr/bin/ip link set dev net0 up
+
ExecStart=/usr/bin/wpa_supplicant -B -i net0 -c /etc/wpa_supplicant.conf # Remove this for wired connections
+
ExecStart=/usr/bin/dhcpcd net0
+
  
ExecStop=/usr/bin/dhcpcd -k net0
+
# ip link set eth0 up
ExecStop=/usr/bin/ip addr flush dev net0
+
# ip addr add 192.168.1.2/24 broadcast 192.168.1.255 dev eth0
ExecStop=/usr/bin/ip link set dev net0 down
+
# ip route add default via 192.168.1.1
  
[Install]
+
{{Tip|If you get the message {{ic|RTNETLINK answers: Network is unreachable}}, try to break up the route creation in the following two parts:
WantedBy=multi-user.target
+
</nowiki>}}
+
  
  # systemctl enable network
+
  # ip route add 192.168.1.1 dev eth0
 +
# ip route add default via 192.168.1.1 dev eth0
 +
}}
  
To test, reboot or stop all other network daemons and run as root:
+
To undo these steps (e.g. before switching to a dynamic IP), first remove any assigned IP address:
# systemctl start network
+
  
=====Using a static IP address=====
+
# ip addr flush dev ''interface''
Create the file {{ic|/etc/systemd/system/network.service}} using your editor of choice. This example uses a static IP address and [[wpa_supplicant]].
+
{{hc|/etc/systemd/system/network.service|<nowiki>
+
[Unit]
+
Description=Wireless Static IP Connectivity
+
Wants=network.target
+
Before=network.target
+
BindsTo=sys-subsystem-net-devices-net0.device
+
After=sys-subsystem-net-devices-net0.device
+
  
[Service]
+
Then remove any assigned gateway:
Type=oneshot
+
RemainAfterExit=yes
+
ExecStart=/usr/bin/ip link set dev net0 up
+
ExecStart=/usr/bin/wpa_supplicant -B -i net0 -c /etc/wpa_supplicant.conf # Remove this for wired connections
+
ExecStart=/usr/bin/ip addr add 192.168.0.10/24 dev net0
+
ExecStart=/usr/bin/ip route add default via 192.168.0.1
+
  
ExecStop=/usr/bin/ip addr flush dev net0
+
# ip route flush dev ''interface''
ExecStop=/usr/bin/ip link set dev net0 down
+
  
[Install]
+
And finally disable the interface:
WantedBy=multi-user.target
+
</nowiki>}}
+
  
Do not forget to enable it!
+
  # ip link set ''interface'' down
  # systemctl enable network
+
  
To test, reboot or make sure all other network daemons are stopped and then run as root
+
For more options, see the {{ic|ip(8)}} man page. These commands can be automated using scripts and [[systemd#Writing unit files|systemd units]].
# systemctl start network
+
  
 
==== Calculating addresses ====
 
==== Calculating addresses ====
  
You can use {{ic|ipcalc}} provided by the {{Pkg|ipcalc}} package to calculate IP broadcast, network, netmask, and host ranges for more advanced configurations. For example, I use ethernet over firewire to connect a windows machine to arch. For security and network organization, I placed them on their own network and configured the netmask and broadcast so that they are the only 2 machines on it. To figure out the netmask and broadcast addresses for this, I used ipcalc, providing it with the IP of the arch firewire nic 10.66.66.1, and specifying ipcalc should create a network of only 2 hosts.
+
You can use {{ic|ipcalc}} provided by the {{Pkg|ipcalc}} package to calculate IP broadcast, network, netmask, and host ranges for more advanced configurations. An example is using Ethernet over Firewire to connect a Windows machine to Linux. To improve security and organization, both machines have their own network with the netmask and broadcast configured accordingly.  
  
{{hc|$ ipcalc -nb 10.66.66.1 -s 1|2=
+
Finding out the respective netmask and broadcast addresses is done with {{ic|ipcalc}}, by specifying the IP of the Linux NIC {{ic|10.66.66.1}} and the number of hosts (here two):
 +
 
 +
{{hc|$ ipcalc -nb 10.66.66.1 -s 1|<nowiki>
 
Address:  10.66.66.1
 
Address:  10.66.66.1
  
Line 326: Line 328:
 
HostMax:  10.66.66.2
 
HostMax:  10.66.66.2
 
Broadcast: 10.66.66.3
 
Broadcast: 10.66.66.3
Hosts/Net: 2                    Class A, Private Internet}}
+
Hosts/Net: 2                    Class A, Private Internet
 +
</nowiki>}}
  
== Load configuration ==
+
== Tips and tricks ==
  
To test your settings either reboot the computer or reload the relevant systemd services:
+
=== ifplugd for laptops ===
  
# systemctl restart dhcpcd@eth0
+
{{Tip|[[dhcpcd]] provides the same feature out of the box.}}
 
+
Try pinging your gateway, DNS server, ISP provider and other Internet sites, in that order, to detect any connection problems along the way, as in this example:
+
 
+
$ ping -c 3 www.google.com
+
 
+
== Additional settings ==
+
 
+
=== ifplugd for laptops ===
+
  
{{Pkg|ifplugd}} in [[Official Repositories]] is a daemon which will automatically configure your Ethernet device when a cable is plugged in and automatically unconfigure it if the cable is pulled. This is useful on laptops with onboard network adapters, since it will only configure the interface when a cable is really connected. Another use is when you just need to restart the network but do not want to restart the computer or do it from the shell.
+
{{Pkg|ifplugd}} in [[official repositories]] is a daemon which will automatically configure your Ethernet device when a cable is plugged in and automatically unconfigure it if the cable is pulled. This is useful on laptops with onboard network adapters, since it will only configure the interface when a cable is really connected. Another use is when you just need to restart the network but do not want to restart the computer or do it from the shell.
  
 
By default it is configured to work for the {{ic|eth0}} device. This and other settings like delays can be configured in {{ic|/etc/ifplugd/ifplugd.conf}}.
 
By default it is configured to work for the {{ic|eth0}} device. This and other settings like delays can be configured in {{ic|/etc/ifplugd/ifplugd.conf}}.
  
{{Note|[[Netctl]] package includes {{ic|netctl-ifplugd@.service}}, otherwise you can use {{ic|ifplugd@.service}} from {{Pkg|ifplugd}} package. Use for example {{ic|systemctl enable ifplugd@eth0.service}}.}}
+
{{Note|[[netctl]] package includes {{ic|netctl-ifplugd@.service}}, otherwise you can use {{ic|ifplugd@.service}} from {{Pkg|ifplugd}} package. For example, [[enable]] {{ic|ifplugd@eth0.service}}.}}
  
 
=== Bonding or LAG ===
 
=== Bonding or LAG ===
  
 +
See [[netctl#Bonding]] or [[Wireless bonding]].
  
You will need {{Pkg|netctl}} from the [[Official Repositories]].
+
=== IP address aliasing ===
  
copy {{ic|/etc/netctl/examples/bonding}} to {{ic|/etc/netctl/bonding}} and edit it, for example, to be the following:
+
IP aliasing is the process of adding more than one IP address to a network interface. With this, one node on a network can have multiple connections to a network, each serving a different purpose. Typical uses are virtual hosting of Web and FTP servers, or reorganizing servers without having to update any other machines (this is especially useful for nameservers).
  
{{hc|/etc/netctl/bonding|2=
+
==== Example ====
Description='Bond Interface'
+
Interface='bond0'
+
Connection=bond
+
BindsToInterfaces=('eth0' 'eth1')
+
IP=dhcp
+
IP6=stateless}}
+
  
Now you can disable and stop your old configuration and  set bonding to be automaticly started:
+
To manually set an alias, for some NIC, use {{Pkg|iproute2}} to execute
  
Disable your old configuration:
+
  # ip addr add 192.168.2.101/24 dev eth0 label eth0:1
  # netctl stop ethernet
+
# netctl disable ethernet
+
Enable and start bonding:
+
# netctl start bonding
+
# netctl enable bonding
+
  
{{Note|To change the bonding mode (default is round robin) to, e.g, active backup:
+
To remove a given alias execute
  
Create {{ic|/etc/modprobe.d/bonding.conf}}:
+
# ip addr del 192.168.2.101/24 dev eth0:1
  
{{hc|/etc/modprobe.d/bonding.conf|2=
+
Packets destined for a subnet will use the primary alias by default. If the destination IP is within a subnet of a secondary alias, then the source IP is set respectively. Consider the case where there is more than one NIC, the default routes can be listed with {{ic|ip route}}.
options bonding mode=2
+
options bonding miimon=100}}
+
  
For more information about the different bonding policies (and other driver settings) see the [http://sourceforge.net/projects/bonding/files/Documentation/ Linux Ethernet Bonding Driver HOWTO] and [http://www.linuxfoundation.org/collaborate/workgroups/networking/bonding The Linux Foundation: bonding].}}
+
=== Change MAC/hardware address ===
  
To check the status and bonding mode:
+
See [[MAC address spoofing]].
  
$ cat /proc/net/bonding/bond0
+
=== Internet sharing ===
  
==== Wired -> Wireless Failover ====
+
See [[Internet sharing]].
  
Using {{ic|bonding}} to fallback to wireless when the wired ethernet goes down, this also detects the presence of either network connection and starts dhcpcd when either or both are connected.
+
=== Router configuration ===
  
You'll need {{Pkg|netctl}}, {{Pkg|ifplugd}}, and {{Pkg|wpa_supplicant}} from the official repositories.
+
See [[Router]].
  
First configure the bonding driver to use active-backup:
+
=== Promiscuous mode ===
  
{{hc|/etc/modprobe.d/bonding.conf|2=
+
Toggling [[wikipedia:Promiscuous_mode|promiscuous mode]] will make a (wireless) NIC forward all traffic it receives to the OS for further processing. This is opposite to "normal mode" where a NIC will drop frames it is not intended to receive. It is most often used for advanced network troubleshooting and [[wikipedia:Packet_sniffing|packet sniffing]].
options bonding mode=active-backup
+
options bonding miimon=100
+
options bonding primary=eth0
+
options bonding max_bonds=0}}
+
  
The `max-bonds` line avoids getting the "Interface bond0 already exists" error.
+
{{hc|/etc/systemd/system/promiscuous@.service|<nowiki>
 
+
Next, configure a {{Pkg|netctl}} profile to enslave the two hardware interfaces:
+
 
+
{{hc|/etc/netctl/failover|2=
+
Description='A wired connection with failover to wireless'
+
Interface='bond0'
+
Connection=bond
+
BindsToInterfaces=('eth0' 'wlan0')
+
IP='no'
+
SkipNoCarrier='no'}}
+
 
+
Enable the profile on startup.
+
 
+
# netctl enable failover
+
 
+
Configure wpa_supplicant to associate with known networks. This can be done with a netctl profile (remember to use IP='no'), a wpa_supplicant service running constantly, or on-demand with wpa_cli. Ways to do this are covered on the [[wpa_supplicant]] page.
+
 
+
Create an {{Pkg|ifplugd}} action for automatic DHCP assignment on the bonded interface:
+
 
+
{{hc|/etc/ifplugd/bond_dhcp.action|2=
+
#!/bin/sh
+
 
+
case "$2" in
+
  up)
+
    systemctl start "dhcpcd@$1.service" && exit 0
+
    ;;
+
  down)
+
    systemctl stop "dhcpcd@$1.service" && exit 0
+
    ;;
+
  *)
+
    echo "Wrong arguments" > /dev/stderr
+
    ;;
+
esac
+
exit 1}}
+
 
+
and make it executable
+
 
+
# chmod +x /etc/ifplugd/bond_dhcp.action
+
 
+
Then create the [[systemd]] service which starts ifplugd for bond0:
+
 
+
{{hc|/etc/systemd/system/net-auto-bonded@.service|2=
+
 
[Unit]
 
[Unit]
Description=Provides automatic dhcp resolution for bonded failover connection
+
Description=Set %i interface in promiscuous mode
Requires=netctl@failover.service
+
After=network.target
After=netctl@failover.service
+
  
 
[Service]
 
[Service]
ExecStart=/usr/bin/ifplugd -i %i -r /etc/ifplugd/bond_dhcp.action -fIns
+
Type=oneshot
 +
ExecStart=/usr/bin/ip link set dev %i promisc on
 +
RemainAfterExit=yes
  
 
[Install]
 
[Install]
WantedBy=multi-user.target}}
+
WantedBy=multi-user.target
 +
</nowiki>}}
  
Enable the net-auto-bonded service and reboot:
+
If you want to enable promiscuous mode on interface {{ic|eth0}} run [[enable]] {{ic|promiscuous@eth0.service}}.
 
+
# systemctl enable net-auto-bonded@bond0.service
+
# reboot
+
 
+
If you have a wired and wireless connection to the same network, you can probably now disconnect and reconnect the wired connection without losing connectivity. In most cases, even streaming music won't skip!
+
 
+
=== IP address aliasing ===
+
 
+
IP aliasing is the process of adding more than one IP address to a network interface. With this, one node on a network can have multiple connections to a network, each serving a different purpose.
+
 
+
To use IP aliasing from [[netcfg]], change {{ic|POST_UP}} and {{ic|PRE_DOWN}} commands in your network profile to set up the additional IP addresses manually. See [https://bbs.archlinux.org/viewtopic.php?pid=1036395#p1036395 here] for details.
+
 
+
==== Example ====
+
 
+
You will need {{Pkg|netctl}} from the [[Official Repositories]].
+
 
+
Prepare the configuration:
+
 
+
{{hc|/etc/netctl/mynetwork|2=
+
 
+
Connection='ethernet'
+
Description='Five different addresses on the same NIC.'
+
Interface='eth0'
+
IP='static'
+
Address=('192.168.1.10' '192.168.178.11' '192.168.1.12' '192.168.1.13' '192.168.1.14' '192.168.1.15')
+
Gateway='192.168.1.1'
+
DNS=('192.168.1.1')
+
Donain=''
+
}}
+
Then simply execute:
+
 
+
$ netctl start mynetwork
+
 
+
=== Change MAC/hardware address ===
+
 
+
See [[MAC Address Spoofing]].
+
 
+
=== Internet Share ===
+
 
+
See [[Internet Share]].
+
 
+
=== Router Configuration ===
+
 
+
See [[Router]].
+
  
 
== Troubleshooting ==
 
== Troubleshooting ==
Line 504: Line 399:
 
=== Swapping computers on the cable modem ===
 
=== Swapping computers on the cable modem ===
  
Most domestic cable ISPs (videotron for example) have the cable modem configured to recognize only one client PC, by the MAC address of its network interface. Once the cable modem has learned the MAC address of the first PC or equipment that talks to it, it will not respond to another MAC address in any way. Thus if you swap one PC for another (or for a router), the new PC (or router) will not work with the cable modem, because the new PC (or router) has a MAC address different from the old one. To reset the cable modem so that it will recognise the new PC, you must power the cable modem off and on again. Once the cable modem has rebooted and gone fully online again (indicator lights settled down), reboot the newly connected PC so that it makes a DHCP request, or manually make it request a new DHCP lease.
+
Some cable ISPs (videotron for example) have the cable modem configured to recognize only one client PC, by the MAC address of its network interface. Once the cable modem has learned the MAC address of the first PC or equipment that talks to it, it will not respond to another MAC address in any way. Thus if you swap one PC for another (or for a router), the new PC (or router) will not work with the cable modem, because the new PC (or router) has a MAC address different from the old one. To reset the cable modem so that it will recognise the new PC, you must power the cable modem off and on again. Once the cable modem has rebooted and gone fully online again (indicator lights settled down), reboot the newly connected PC so that it makes a DHCP request, or manually make it request a new DHCP lease.
  
If this method does not work, you will need to clone the MAC address of the original machine. See also [[Configuring Network#Change MAC/hardware address|Change MAC/hardware address]].
+
If this method does not work, you will need to clone the MAC address of the original machine. See also [[#Change MAC/hardware address]].
  
 
=== The TCP window scaling problem ===
 
=== The TCP window scaling problem ===
Line 512: Line 407:
 
TCP packets contain a "window" value in their headers indicating how much data the other host may send in return. This value is represented with only 16 bits, hence the window size is at most 64Kb. TCP packets are cached for a while (they have to be reordered), and as memory is (or used to be) limited, one host could easily run out of it.
 
TCP packets contain a "window" value in their headers indicating how much data the other host may send in return. This value is represented with only 16 bits, hence the window size is at most 64Kb. TCP packets are cached for a while (they have to be reordered), and as memory is (or used to be) limited, one host could easily run out of it.
  
Back in 1992, as more and more memory became available, [http://www.faqs.org/rfcs/rfc1323.html RFC 1323] was written to improve the situation: Window Scaling. The "window" value, provided in all packets, will be modified by a Scale Factor defined once, at the very beginning of the connection.
+
Back in 1992, as more and more memory became available, [http://www.faqs.org/rfcs/rfc1323.html RFC 1323] was written to improve the situation: Window Scaling. The "window" value, provided in all packets, will be modified by a Scale Factor defined once, at the very beginning of the connection. That 8-bit Scale Factor allows the Window to be up to 32 times higher than the initial 64Kb.
  
That 8-bit Scale Factor allows the Window to be up to 32 times higher than the initial 64Kb.
+
It appears that some broken routers and firewalls on the Internet are rewriting the Scale Factor to 0 which causes misunderstandings between hosts. The Linux kernel 2.6.17 introduced a new calculation scheme generating higher Scale Factors, virtually making the aftermaths of the broken routers and firewalls more visible.
 
+
It appears that some broken routers and firewalls on the Internet are rewriting the Scale Factor to 0 which causes misunderstandings between hosts.
+
 
+
The Linux kernel 2.6.17 introduced a new calculation scheme generating higher Scale Factors, virtually making the aftermaths of the broken routers and firewalls more visible.
+
  
 
The resulting connection is at best very slow or broken.
 
The resulting connection is at best very slow or broken.
Line 530: Line 421:
 
If you cannot browse any website, but you can ping some random hosts, chances are great that you're experiencing this problem: ping uses ICMP and is not affected by TCP problems.
 
If you cannot browse any website, but you can ping some random hosts, chances are great that you're experiencing this problem: ping uses ICMP and is not affected by TCP problems.
  
You can try to use Wireshark. You might see successful UDP and ICMP communications but unsuccessful TCP communications (only to foreign hosts).
+
You can try to use [[Wireshark]]. You might see successful UDP and ICMP communications but unsuccessful TCP communications (only to foreign hosts).
  
==== How to fix it (The bad way) ====
+
==== Ways of fixing it ====
  
To fix it the bad way, you can change the tcp_rmem value, on which Scale Factor calculation is based. Although it should work for most hosts, it is not guaranteed, especially for very distant ones.
+
===== Bad =====
 +
 
 +
To fix it the bad way, you can change the {{ic|tcp_rmem}} value, on which Scale Factor calculation is based. Although it should work for most hosts, it is not guaranteed, especially for very distant ones.
  
 
  # echo "4096 87380 174760" > /proc/sys/net/ipv4/tcp_rmem
 
  # echo "4096 87380 174760" > /proc/sys/net/ipv4/tcp_rmem
  
==== How to fix it (The good way) ====
+
===== Good =====
  
Simply disable Window Scaling. Since Window Scaling is a nice TCP feature, it may be uncomfortable to disable it, especially if you cannot fix the broken router. There are several ways to disable Window Scaling, and it seems that the most bulletproof way (which will work with most kernels) is to add the following line to {{ic|/etc/sysctl.conf}} (see also [[sysctl]])
+
Simply disable Window Scaling. Since Window Scaling is a nice TCP feature, it may be uncomfortable to disable it, especially if you cannot fix the broken router. There are several ways to disable Window Scaling, and it seems that the most bulletproof way (which will work with most kernels) is to add the following line to {{ic|/etc/sysctl.d/99-disable_window_scaling.conf}} (see also [[sysctl]]):
  
 
  net.ipv4.tcp_window_scaling = 0
 
  net.ipv4.tcp_window_scaling = 0
  
==== How to fix it (The best way) ====
+
===== Best =====
  
 
This problem is caused by broken routers/firewalls, so let's change them. Some users have reported that the broken router was their very own DSL router.
 
This problem is caused by broken routers/firewalls, so let's change them. Some users have reported that the broken router was their very own DSL router.
Line 556: Line 449:
 
=== Realtek no link / WOL problem ===
 
=== Realtek no link / WOL problem ===
  
Users with Realtek 8168 8169 8101 8111(C) based NICs (cards / and on-board) may notice a problem where the NIC seems to be disabled on boot and has no Link light. This can usually be found on a dual boot system where Windows is also installed. It seems that using the offical Realtek drivers (dated anything after May 2007) under Windows is the cause. These newer drivers disable the Wake-On-LAN feature by disabling the NIC at Windows shutdown time, where it will remain disabled until the next time Windows boots. You will be able to notice if this problem is affecting you if the Link light remains off until Windows boots up; during Windows shutdown the Link light will switch off. Normal operation should be that the link light is always on as long as the system is on, even during POST. This problem will also affect other operative systems without newer drivers (eg. Live CDs). Here are a few fixes for this problem:
+
Users with Realtek 8168 8169 8101 8111(C) based NICs (cards / and on-board) may notice a problem where the NIC seems to be disabled on boot and has no Link light. This can usually be found on a dual boot system where Windows is also installed. It seems that using the offical Realtek drivers (dated anything after May 2007) under Windows is the cause. These newer drivers disable the Wake-On-LAN feature by disabling the NIC at Windows shutdown time, where it will remain disabled until the next time Windows boots. You will be able to notice if this problem is affecting you if the Link light remains off until Windows boots up; during Windows shutdown the Link light will switch off. Normal operation should be that the link light is always on as long as the system is on, even during POST. This problem will also affect other operating systems without newer drivers (eg. Live CDs). Here are a few fixes for this problem.
 +
 
 +
==== Enable the NIC directly in Linux ====
 +
 
 +
Follow [[#Enabling and disabling network interfaces]] to enable the interface.
  
==== Method 1 - Rollback/change Windows driver ====
+
==== Rollback/change Windows driver ====
  
 
You can roll back your Windows NIC driver to the Microsoft provided one (if available), or roll back/install an official Realtek driver pre-dating May 2007 (may be on the CD that came with your hardware).
 
You can roll back your Windows NIC driver to the Microsoft provided one (if available), or roll back/install an official Realtek driver pre-dating May 2007 (may be on the CD that came with your hardware).
  
==== Method 2 - Enable WOL in Windows driver ====
+
==== Enable WOL in Windows driver ====
  
Probably the best and the fastest fix is to change this setting in the Windows driver. This way it should be fixed system-wide and not only under Arch (eg. live CDs, other operative systems). In Windows, under Device Manager, find your Realtek network adapter and double-click it. Under the Advanced tab, change "Wake-on-LAN after shutdown" to Enable.
+
Probably the best and the fastest fix is to change this setting in the Windows driver. This way it should be fixed system-wide and not only under Arch (eg. live CDs, other operating systems). In Windows, under Device Manager, find your Realtek network adapter and double-click it. Under the "Advanced" tab, change "Wake-on-LAN after shutdown" to "Enable".
  
In Windows XP (example)
+
In Windows XP (example):
  Right click my computer
+
 
  --> Hardware tab
+
  Right click my computer and choose "Properties"
 +
  --> "Hardware" tab
 
   --> Device Manager
 
   --> Device Manager
 
     --> Network Adapters
 
     --> Network Adapters
Line 578: Line 476:
 
{{Note|Newer Realtek Windows drivers (tested with ''Realtek 8111/8169 LAN Driver v5.708.1030.2008'', dated 2009/01/22, available from GIGABYTE) may refer to this option slightly differently, like ''Shutdown Wake-On-LAN --> Enable''. It seems that switching it to {{ic|Disable}} has no effect (you will notice the Link light still turns off upon Windows shutdown). One rather dirty workaround is to boot to Windows and just reset the system (perform an ungraceful restart/shutdown) thus not giving the Windows driver a chance to disable LAN. The Link light will remain on and the LAN adapter will remain accessible after POST - that is until you boot back to Windows and shut it down properly again.}}
 
{{Note|Newer Realtek Windows drivers (tested with ''Realtek 8111/8169 LAN Driver v5.708.1030.2008'', dated 2009/01/22, available from GIGABYTE) may refer to this option slightly differently, like ''Shutdown Wake-On-LAN --> Enable''. It seems that switching it to {{ic|Disable}} has no effect (you will notice the Link light still turns off upon Windows shutdown). One rather dirty workaround is to boot to Windows and just reset the system (perform an ungraceful restart/shutdown) thus not giving the Windows driver a chance to disable LAN. The Link light will remain on and the LAN adapter will remain accessible after POST - that is until you boot back to Windows and shut it down properly again.}}
  
==== Method 3 - Newer Realtek Linux driver ====
+
==== Newer Realtek Linux driver ====
  
Any newer driver for these Realtek cards can be found for Linux on the realtek site. (untested but believed to also solve the problem).
+
Any newer driver for these Realtek cards can be found for Linux on the realtek site (untested but believed to also solve the problem).
  
==== Method 4 - Enable ''LAN Boot ROM'' in BIOS/CMOS ====
+
==== Enable ''LAN Boot ROM'' in BIOS/CMOS ====
  
 
It appears that setting ''Integrated Peripherals --> Onboard LAN Boot ROM --> Enabled'' in BIOS/CMOS reactivates the Realtek LAN chip on system boot-up, despite the Windows driver disabling it on OS shutdown.
 
It appears that setting ''Integrated Peripherals --> Onboard LAN Boot ROM --> Enabled'' in BIOS/CMOS reactivates the Realtek LAN chip on system boot-up, despite the Windows driver disabling it on OS shutdown.
<br><small>This was tested successfully multiple times with GIGABYTE system board GA-G31M-ES2L with BIOS version F8 released on 2009/02/05. YMMV.</small>
 
  
=== DLink G604T/DLink G502T DNS problem ===
+
{{Note|This was tested several times on a GIGABYTE GA-G31M-ES2L motherboard, BIOS version F8 released on 2009/02/05.}}
  
Users with a DLink G604T/DLink G502T router, using DHCP and have firmware v2.00+ (typically users with AUS firmware) may have problems with certain programs not resolving the DNS. One of these programs are unfortunatley pacman. The problem is basically the router in certain situations is not sending the DNS properly to DHCP, which causes programs to try and connect to servers with an IP address of 1.0.0.0 and fail with a connection timed out error
+
=== No interface with Atheros chipsets ===
  
==== How to diagnose the problem ====
+
Users of some Atheros ethernet chips are reporting it does not work out-of-the-box (with installation media of February 2014). The working solution for this is to install {{AUR|backports-patched}}.
  
The best way to diagnose the problem is to use Firefox/Konqueror/links/seamonkey and to enable wget for pacman. If this is a fresh install of Arch Linux, then you may want to consider installing {{ic|links}} through the live CD.
+
=== Broadcom BCM57780 ===
  
Firstly, enable wget for pacman (since it gives us info about pacman when it is downloading packages)
+
This Broadcom chipset sometimes does not behave well unless you specify the order of the modules to be loaded. The modules are {{ic|broadcom}} and {{ic|tg3}}, the former needing to be loaded first.
Open {{ic|/etc/pacman.conf}} with your favourite editor and uncomment the following line (remove the # if it is there)
+
  
XferCommand=/usr/bin/wget --passive-ftp -c -O %o %u
+
These steps should help if your computer has this chipset:
  
While you are editing {{ic|/etc/pacman.conf}}, check the default mirror that pacman uses to download packages.
+
* Find your NIC in ''lspci'' output:
  
Now open up the default mirror in an Internet browser to see if the mirror actually works. If it does work, then do {{ic|pacman -Syy}} (otherwise pick another working mirror and set it to the pacman default). If you get something similar to the following (notice the 1.0.0.0),
+
$ lspci | grep Ethernet
 +
02:00.0 Ethernet controller: Broadcom Corporation NetLink BCM57780 Gigabit Ethernet PCIe (rev 01)
  
<nowiki>ftp://mirror.pacific.net.au/linux/archlinux/extra/os/i686/extra.db.tar.gz</nowiki>
+
* If your wired networking is not functioning in some way or another, try unplugging your cable then doing the following:
            => '/var/lib/pacman/community.db.tar.gz.part'
+
Resolving mirror.pacific.net.au... 1.0.0.0
+
  
then you most likely have this problem. The 1.0.0.0 means it is unable to resolve DNS, so we must add it to {{ic|/etc/resolv.conf}}.
+
# modprobe -r tg3
 +
# modprobe broadcom
 +
# modprobe tg3
  
==== How to fix it ====
+
* Plug your network cable in. If this solves your problems you can make this permanent by adding {{ic|broadcom}} and {{ic|tg3}} (in this order) to the {{ic|MODULES}} array in {{ic|/etc/mkinitcpio.conf}}:
  
Basically what we need to do is to manually add the DNS servers to our {{ic|/etc/resolv.conf}} file. The problem is that DHCP automatically deletes and replaces this file on boot, so we need to edit {{ic|/etc/conf.d/dhcpcd}} and change the flags to stop DHCP from doing this.
+
MODULES=".. broadcom tg3 .."
  
When you open {{ic|/etc/conf.d/dhcpcd}}, you should see something close to the following:
+
* Rebuild the initramfs:
  
  DHCPCD_ARGS="-t 30 -h $HOSTNAME"
+
  # mkinitcpio -p linux
  
Add the {{ic|-R}} flag to the arguments, e.g.,
+
* Alternatively, you can create an {{ic|/etc/modprobe.d/broadcom.conf}}:
  
  DHCPCD_ARGS="-R -t 30 -h $HOSTNAME"
+
  softdep tg3 pre: broadcom
  
{{Note|1=If you are using {{Pkg|dhcpcd}} >= 4.0.2, the {{ic|-R}} flag has been deprecated. Please see the [[#For DHCP assigned IP address]] section for information on how to use a custom {{ic|/etc/resolv.conf}} file.}}
+
{{Note|These methods may work for other chipsets, such as BCM57760.}}
  
Save and close the file; now open {{ic|/etc/resolv.conf}}. You should see a single nameserver (most likely 10.1.1.1). This is the gateway to your router, which we need to connect to in order to get the DNS servers of your ISP. Paste the IP address into your browser and log in to your router. Go to the DNS section, and you should see an IP address in the Primary DNS Server field; copy it and paste it as a nameserver '''ABOVE''' the current gateway one.
+
=== Realtek RTL8111/8168B ===
  
For example, {{ic|/etc/resolv.conf}} should look something along the lines of:
+
{{hc|<nowiki># lspci | grep Ethernet</nowiki>|
 
+
03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 02)
nameserver 10.1.1.1
+
}}
 
+
If my primary DNS server is 211.29.132.12, then change {{ic|/etc/resolv.conf}} to:
+
 
+
nameserver 211.29.132.12
+
nameserver 10.1.1.1
+
 
+
Now restart the network daemon by running {{ic|systemctl restart dhcpcd@<interface>}} and do {{ic|pacman -Syy}}. If it syncs correctly with the server, then the problem is solved.
+
 
+
==== More about it ====
+
 
+
This is the whirlpool forum (Australian ISP community) which talks about and gives the same solution to the problem:
+
 
+
http://forums.whirlpool.net.au/forum-replies-archive.cfm/461625.html
+
 
+
=== Check DHCP problem by releasing IP first ===
+
 
+
Problem may occur when DHCP get wrong IP assignment. For example when two routers are tied together through VPN. The router that is connected to me by VPN may assigning IP address. To fix it. On a console, as root, release IP address:
+
 
+
# dhcpcd -k
+
 
+
Then request a new one:
+
 
+
# dhcpcd
+
 
+
Maybe you had to run those two commands many times.
+
 
+
 
+
=== No eth0 with Atheros AR8161 ===
+
 
+
With the Atheros AR8161 Gigabit Ethernet card, the ethernet connection is not working out-of-the-box (with the installation media of March 2013). The module "alx" needs to be loaded but is not present.
+
 
+
The driver from [http://linuxwireless.org/en/users/Download/stable/#compat-wireless_stable_releases compat-wireless] (that has become [https://backports.wiki.kernel.org/index.php/Releases compat-drives] since linux 3.7) need to be installed. The "-u" postfix annotates that Qualcomm have applied a driver under a unified driver.
+
  $ wget https://www.kernel.org/pub/linux/kernel/projects/backports/2013/03/28/compat-drivers-2013-03-28-5-u.tar.bz2
+
  $ tar xjf compat*
+
  $ cd compat*
+
  $ ./scripts/driver-select alx
+
  $ make
+
  $ sudo make install
+
  $ sudo modprobe alx
+
 
+
The alx driver has not been added to Linux kernel due to various problems. Compatibility between the different kernel versions has been spotty. For better support follow the [http://lists.infradead.org/mailman/listinfo/unified-drivers mailing list]and [http://www.linuxfoundation.org/collaborate/workgroups/networking/alx alx page]for latest working solution for alx.
+
 
+
The driver must be built and installed after every kernel change.
+
 
+
Alternatively you can use the AUR package for [https://aur.archlinux.org/packages/compat-drivers-patched/ compat drivers], which installs many other drivers.
+
 
+
=== No eth0 with Atheros AR9485 ===
+
 
+
The ethernet (eth0) for Atheros AR9485 are not working out-of-the-box (with installation media of March 2013). The working solution for this is to install the package [https://aur.archlinux.org/packages/compat-drivers-patched/ compat-drivers-patched] from AUR.
+
 
+
=== No carrier / no connection after suspend ===
+
After suspend to RAM no connection is found although the network cable is plugged in.
+
This may be caused by PCI power management. What is the output of
+
 
+
# ip link show eth0
+
 
+
If the line contains "NO-CARRIER" even though there's a cable connected to your eth0 port, it is possible that the device was auto-suspended and the media sense feature doesn't work. To solve this, first you need to find your ethernet controllers PCI address by
+
 
+
# lspci
+
 
+
This should look similar to this:
+
 
+
...
+
00:19.0 Ethernet controller: Intel Corporation 82577LM Gigabit Network Connection (rev 06)
+
...
+
 
+
So the address is 00:19.0.
+
Now check the PM status of the device by issuing
+
 
+
# cat "/sys/bus/pci/devices/0000:00:19.0/power/control"
+
  
substituting 00:19.0 with the address obtained from lspci.
+
The adapter should be recognized by the {{ic|r8169}} module. However, with some chip revisions the connection may go off and on all the time. The alternative {{Pkg|r8168}} can be found in the [[official repositories]] and should be used for a reliable connection in this case. [[Blacklist]] {{ic|r8169}}, if {{Pkg|r8168}} is not automatically loaded by [[udev]], see [[Kernel modules#Automatic module handling]].
If the output reads "auto", you can try to bring the device out of suspend by
+
  
# echo on > "/sys/bus/pci/devices/0000:00:19.0/power/control"
+
{{Accuracy|"some revisions", no proof the driver is the cause, and not e.g poorly configured DNS servers}}
  
Don't forget to substitute the address again.
+
Another fault in the drivers for some revisions of this adapter is poor IPv6 support. [[IPv6#Disable functionality]] can be helpful if you encounter issues such as hanging webpages and slow speeds.
  
{{Note|1=This appears to be a bug in kernel 3.8.4.1- (3.8.8.1 is still affected): [https://bbs.archlinux.org/viewtopic.php?id=159837&p=2 Forum discussion.] It also appears a fix is [https://lkml.org/lkml/2013/1/18/147 on the way. (It will be likely fixed in 3.9.)] In the meantime, the above is a suitable workaround.}}
+
=== Gigabyte Motherboard with Realtek 8111/8168/8411 ===
 +
With motherboards such as the Gigabyte GA-990FXA-UD3, booting with IOMMU off (which can be the default) will cause the network interface to be unreliable, often failing to connect or connecting but allowing no throughput. This will apply not only to the onboard NIC, but any other pci-NIC you put in the box because the IOMMU setting affects the entire network interface on the board. Enabling IOMMU and booting with the install media will throw AMD I-10/xhci page faults for a second, but then boot normally, resulting in a fully functional onboard NIC (even with the r8169 module).
  
=== PC Pingable by IP but not by hostname? ===
+
When configuring the boot process for your installation, add {{ic|1=iommu=soft}} as a [[kernel parameter]] to eliminate the error messages on boot and restore USB3.0 functionality.
This issue hunted me for months! Turns out to be a very simple fix IF you are using samba as well. Usually people only start smbd which is enough for network access to work, but does not advocate the pc's name to the router. nmbd is doing that so you should always have:
+
systemctl enable smbd.service
+
systemctl enable nmbd.service
+
  
Which makes them run at startup. If you don't want to restart then you can start then right away with:
+
== See also ==
systemctl start smbd.service
+
systemctl start nmbd.service
+
  
And that makes the computer available by name on the network.
+
* [https://www.debian.org/doc/manuals/debian-reference/ch05.en.html Debian Reference: Network setup]
 +
* [https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Networking_Guide/ RHEL7: Networking Guide]

Latest revision as of 12:52, 21 September 2016

This page explains how to set up a wired connection to a network. If you need to set up wireless networking see the Wireless network configuration page.

Check the connection

The basic installation procedure typically has a functional network configuration. Use ping(8) to check the connection:

$ ping www.google.com
PING www.l.google.com (74.125.132.105) 56(84) bytes of data.
64 bytes from wb-in-f105.1e100.net (74.125.132.105): icmp_req=1 ttl=50 time=17.0 ms
...

If the ping is successful (you see 64 bytes messages as above), then the network is configured. Press Control-C to stop the ping.

If the ping failed with an Unknown hosts error, it means that your machine was unable to resolve this domain name. It may be related to your service provider or your router/gateway. Try pinging a static IP address to prove that your machine has access to the Internet:

$ ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_req=1 ttl=53 time=52.9 ms
...

If you are able to ping 8.8.8.8 but not www.google.com, check your DNS configuration. See resolv.conf for details. The hosts line in /etc/nsswitch.conf is another place you can check.

If not, check for cable issues before diagnosing further.

Note:
  • If you receive an error like ping: icmp open socket: Operation not permitted when executing ping, try to re-install the iputils package.
  • The -c num option can be used to make exactly num pings, otherwise it pings infinitely and has to be terminated manually. See man ping for more information.
  • 8.8.8.8 is a static address that is easy to remember. It is the address of Google's primary DNS server, therefore it can be considered reliable, and is generally not blocked by content filtering systems and proxies.

Set the hostname

A hostname is a unique name created to identify a machine on a network, configured in /etc/hostname—see hostname(5) and hostname(7) for details. The file can contain the system's domain name, if any. To set the hostname, edit /etc/hostname to include a single line with myhostname:

/etc/hostname
myhostname
Tip: For advice on choosing a hostname, see RFC 1178.

Alternatively, using hostnamectl(1):

# hostnamectl set-hostname myhostname

To temporarily set the hostname (until reboot), use hostname(1) from inetutils:

# hostname myhostname

To set the "pretty" hostname and other machine metadata, see machine-info(5).

Local network hostname resolution

The pre-requisite is to #Set the hostname, after which hostname resolution works on the local system itself:

$ ping myhostname
PING myhostname (192.168.1.2) 56(84) bytes of data.
64 bytes from myhostname (192.168.1.2): icmp_seq=1 ttl=64 time=0.043 ms

To allow other machines to address the host by name, it is necessary to either:

  • Configure the hosts(5) file, or
  • Enable a service which resolves the hostname.
Note: systemd provides hostname resolution via the myhostname nss module, enabled by default in /etc/nsswitch.conf. However, clients may still rely on /etc/hosts, see [1] [2] for examples.

To configure the hosts file, add the following line to /etc/hosts:

127.0.1.1	myhostname.localdomain	myhostname

As a result the system resolves to both entries:

$ getent hosts 
127.0.0.1       localhost
127.0.1.1       myhostname.localdomain myhostname

For a system with a permanent IP address, that permanent IP address should be used instead of 127.0.1.1.

Note: Another option is to set up a full DNS server such as BIND or Unbound, but that is overkill and too complex for most systems. For small networks and dynamic flexibility with hosts joining and leaving the network zero-configuration networking services may be more applicable:
  • Samba provides hostname resolution via Microsoft's NetBIOS. It only requires installation of samba and enabling of the nmbd.service service. Computers running Windows, macOS, or Linux with nmbd running, will be able to find your machine.
  • Avahi provides hostname resolution via zeroconf, also known as Avahi or Bonjour. It requires slightly more complex configuration than Samba: see Avahi#Hostname resolution for details. Computers running macOS, or Linux with an Avahi daemon running, will be able to find your machine. Windows does not have an built-in Avahi client or daemon.

Device driver

Check the status

udev should detect your network interface card (see Wikipedia:Network interface controller) and automatically load the necessary module at start up. Check the "Ethernet controller" entry (or similar) from the lspci -v output. It should tell you which kernel module contains the driver for your network device. For example:

$ lspci -v
02:00.0 Ethernet controller: Attansic Technology Corp. L1 Gigabit Ethernet Adapter (rev b0)
 	...
 	Kernel driver in use: atl1
 	Kernel modules: atl1

Next, check that the driver was loaded via dmesg | grep module_name. For example:

$ dmesg | grep atl1
    ...
    atl1 0000:02:00.0: eth0 link is up 100 Mbps full duplex

Skip the next section if the driver was loaded successfully. Otherwise, you will need to know which module is needed for your particular model.

Load the module

Search in the Internet for the right module/driver for the chipset. Some common modules are 8139too for cards with a Realtek chipset, or sis900 for cards with a SiS chipset. Once you know which module to use, try to load it manually. If you get an error saying that the module was not found, it's possible that the driver is not included in Arch kernel. You may search the AUR for the module name.

If udev is not detecting and loading the proper module automatically during bootup, see Kernel modules#Automatic module handling.

Network interfaces

Device names

For computers with multiple NICs, it is important to have fixed device names. Many configuration problems are caused by interface name changing.

udev is responsible for which device gets which name. Systemd v197 introduced Predictable Network Interface Names, which automatically assigns static names to network devices. Interfaces are now prefixed with en (wired/Ethernet), wl (wireless/WLAN), or ww (WWAN) followed by an automatically generated identifier, creating an entry such as enp0s25. This behavior may be disabled by adding net.ifnames=0 to the kernel parameters.

Note: When changing the interface naming scheme, do not forget to update all network-related configuration files and custom systemd unit files to reflect the change. Specifically, if you have netctl static profiles enabled, run netctl reenable profile to update the generated service file.

Get current device names

Current NIC names can be found via sysfs or ip link. For example:

$ ls /sys/class/net
lo enp0s3
$ ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 08:00:27:23:6f:3a brd ff:ff:ff:ff:ff:ff

Wireless device names can also be retrieved using iw dev. See Wireless network configuration#Getting some useful information for details.

Change device name

You can change the device name by defining the name manually with an udev-rule. For example:

/etc/udev/rules.d/10-network.rules
SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="aa:bb:cc:dd:ee:ff", NAME="net1"
SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="ff:ee:dd:cc:bb:aa", NAME="net0"

These rules will be applied automatically at boot.

A couple of things to note:

  • To get the MAC address of each card, use this command: cat /sys/class/net/device_name/address
  • Make sure to use the lower-case hex values in your udev rules. It doesn't like upper-case.

If the network card has a dynamic MAC, you can use DEVPATH, for example:

/etc/udev/rules.d/10-network.rules
SUBSYSTEM=="net", DEVPATH=="/devices/platform/wemac.*", NAME="int"
SUBSYSTEM=="net", DEVPATH=="/devices/pci*/*1c.0/*/net/*", NAME="en"

The device path should match both the new and old device name, since the rule may be executed more than once on bootup. For example, in the second rule, "/devices/pci*/*1c.0/*/net/enp*" would be wrong since it will stop matching once the name is changed to en. Only the system-default rule will fire the second time around, causing the name to be changed back to e.g. enp1s0.

To test your rules, they can be triggered directly from userspace, e.g. with udevadm --debug test /sys/DEVPATH. Remember to first take down the interface you are trying to rename (e.g. ip link set enp1s0 down).

Note: When choosing the static names it should be avoided to use names in the format of "ethX" and "wlanX", because this may lead to race conditions between the kernel and udev during boot. Instead, it is better to use interface names that are not used by the kernel as default, e.g.: net0, net1, wifi0, wifi1. For further details please see the systemd documentation.

Reverting to traditional device names

If you would prefer to retain traditional interface names such as eth0, Predictable Network Interface Names can be disabled with the following:

 # ln -s /dev/null /etc/udev/rules.d/80-net-setup-link.rules

Set device MTU and queue length

You can change the device MTU and queue length by defining manually with an udev-rule. For example:

/etc/udev/rules.d/10-network.rules
ACTION=="add", SUBSYSTEM=="net", KERNEL=="wl*", ATTR{mtu}="1480", ATTR{tx_queue_len}="2000"

Enabling and disabling network interfaces

You can activate or deactivate network interfaces using:

# ip link set eth0 up
# ip link set eth0 down

To check the result:

$ ip link show dev eth0
2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master br0 state UP mode DEFAULT qlen 1000
...
Note: If your default route is through interface eth0, taking it down will also remove the route, and bringing it back up will not automatically reestablish the default route. See #Manual assignment for reestablishing it.

Configure the IP address

Warning: Use a single method to manage the network, as several methods may conflict.

You have two options: a dynamically assigned address using DHCP, or an unchanging "static" address. See also List of applications#Network managers.

Dynamic IP address

systemd-networkd

An easy way to setup DHCP for simple requirements is to use systemd-networkd service provided by systemd. See systemd-networkd#Basic DHCP network.

dhcpcd

dhcpcd is the default client in Arch Linux to setup DHCP on the installation ISO. It is a powerful tool with many configurable DHCP client options. See dhcpcd#Running on how to activate it for an interface.

dhclient

dhclient is the Internet Systems Consortium DHCP client. Enable the dhclient@interface.service, where interface is a wired #Device name. See dhclient(8) and dhclient.conf(5) for details.

netctl

netctl is a CLI-based tool for configuring and managing network connections through user-created profiles. Create a profile as shown in netctl#Example profiles, then enable it as described in netctl#Basic method.

Static IP address

A static IP address can be configured with most standard Arch Linux networking tools. Independent of the tool you choose, you will probably need to be prepared with the following information:

If you are running a private network, it is safe to use IP addresses in 192.168.*.* for your IP addresses, with a subnet mask of 255.255.255.0 and a broadcast address of 192.168.*.255. The gateway is usually 192.168.*.1 or 192.168.*.254.

Warning:
  • Make sure manually assigned IP addresses do not conflict with DHCP assigned ones. See this forum thread.
  • If you share your Internet connection from a Windows machine without a router, be sure to use static IP addresses on both computers to avoid LAN problems.
Tip: Addresses can be calculated with the ipcalc package; see #Calculating addresses.

netctl

To create a netctl profile with a static IP, set the IP=static option as well as Address, Gateway, and DNS. See netctl#Wired.

systemd-networkd

The systemd-networkd service provided by systemd can set up a static IP using a simple configuration file. See systemd-networkd#Wired adapter using a static IP.

dhcpcd

See dhcpcd#Static profile.

Manual assignment

It is possible to manually set up a static IP using only the iproute2 package. This is a good way to test connection settings since the connection made using this method will not persist across reboots. First enable the network interface:

# ip link set interface up

Assign a static IP address in the console:

# ip addr add IP_address/subnet_mask broadcast broadcast_address dev interface

Then add your gateway IP address:

# ip route add default via default_gateway

For example:

# ip link set eth0 up
# ip addr add 192.168.1.2/24 broadcast 192.168.1.255 dev eth0
# ip route add default via 192.168.1.1
Tip: If you get the message RTNETLINK answers: Network is unreachable, try to break up the route creation in the following two parts:
# ip route add 192.168.1.1 dev eth0
# ip route add default via 192.168.1.1 dev eth0

To undo these steps (e.g. before switching to a dynamic IP), first remove any assigned IP address:

# ip addr flush dev interface

Then remove any assigned gateway:

# ip route flush dev interface

And finally disable the interface:

# ip link set interface down

For more options, see the ip(8) man page. These commands can be automated using scripts and systemd units.

Calculating addresses

You can use ipcalc provided by the ipcalc package to calculate IP broadcast, network, netmask, and host ranges for more advanced configurations. An example is using Ethernet over Firewire to connect a Windows machine to Linux. To improve security and organization, both machines have their own network with the netmask and broadcast configured accordingly.

Finding out the respective netmask and broadcast addresses is done with ipcalc, by specifying the IP of the Linux NIC 10.66.66.1 and the number of hosts (here two):

$ ipcalc -nb 10.66.66.1 -s 1
Address:   10.66.66.1

Netmask:   255.255.255.252 = 30
Network:   10.66.66.0/30
HostMin:   10.66.66.1
HostMax:   10.66.66.2
Broadcast: 10.66.66.3
Hosts/Net: 2                     Class A, Private Internet

Tips and tricks

ifplugd for laptops

Tip: dhcpcd provides the same feature out of the box.

ifplugd in official repositories is a daemon which will automatically configure your Ethernet device when a cable is plugged in and automatically unconfigure it if the cable is pulled. This is useful on laptops with onboard network adapters, since it will only configure the interface when a cable is really connected. Another use is when you just need to restart the network but do not want to restart the computer or do it from the shell.

By default it is configured to work for the eth0 device. This and other settings like delays can be configured in /etc/ifplugd/ifplugd.conf.

Note: netctl package includes netctl-ifplugd@.service, otherwise you can use ifplugd@.service from ifplugd package. For example, enable ifplugd@eth0.service.

Bonding or LAG

See netctl#Bonding or Wireless bonding.

IP address aliasing

IP aliasing is the process of adding more than one IP address to a network interface. With this, one node on a network can have multiple connections to a network, each serving a different purpose. Typical uses are virtual hosting of Web and FTP servers, or reorganizing servers without having to update any other machines (this is especially useful for nameservers).

Example

To manually set an alias, for some NIC, use iproute2 to execute

# ip addr add 192.168.2.101/24 dev eth0 label eth0:1

To remove a given alias execute

# ip addr del 192.168.2.101/24 dev eth0:1

Packets destined for a subnet will use the primary alias by default. If the destination IP is within a subnet of a secondary alias, then the source IP is set respectively. Consider the case where there is more than one NIC, the default routes can be listed with ip route.

Change MAC/hardware address

See MAC address spoofing.

Internet sharing

See Internet sharing.

Router configuration

See Router.

Promiscuous mode

Toggling promiscuous mode will make a (wireless) NIC forward all traffic it receives to the OS for further processing. This is opposite to "normal mode" where a NIC will drop frames it is not intended to receive. It is most often used for advanced network troubleshooting and packet sniffing.

/etc/systemd/system/promiscuous@.service
[Unit]
Description=Set %i interface in promiscuous mode
After=network.target

[Service]
Type=oneshot
ExecStart=/usr/bin/ip link set dev %i promisc on
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

If you want to enable promiscuous mode on interface eth0 run enable promiscuous@eth0.service.

Troubleshooting

Swapping computers on the cable modem

Some cable ISPs (videotron for example) have the cable modem configured to recognize only one client PC, by the MAC address of its network interface. Once the cable modem has learned the MAC address of the first PC or equipment that talks to it, it will not respond to another MAC address in any way. Thus if you swap one PC for another (or for a router), the new PC (or router) will not work with the cable modem, because the new PC (or router) has a MAC address different from the old one. To reset the cable modem so that it will recognise the new PC, you must power the cable modem off and on again. Once the cable modem has rebooted and gone fully online again (indicator lights settled down), reboot the newly connected PC so that it makes a DHCP request, or manually make it request a new DHCP lease.

If this method does not work, you will need to clone the MAC address of the original machine. See also #Change MAC/hardware address.

The TCP window scaling problem

TCP packets contain a "window" value in their headers indicating how much data the other host may send in return. This value is represented with only 16 bits, hence the window size is at most 64Kb. TCP packets are cached for a while (they have to be reordered), and as memory is (or used to be) limited, one host could easily run out of it.

Back in 1992, as more and more memory became available, RFC 1323 was written to improve the situation: Window Scaling. The "window" value, provided in all packets, will be modified by a Scale Factor defined once, at the very beginning of the connection. That 8-bit Scale Factor allows the Window to be up to 32 times higher than the initial 64Kb.

It appears that some broken routers and firewalls on the Internet are rewriting the Scale Factor to 0 which causes misunderstandings between hosts. The Linux kernel 2.6.17 introduced a new calculation scheme generating higher Scale Factors, virtually making the aftermaths of the broken routers and firewalls more visible.

The resulting connection is at best very slow or broken.

How to diagnose the problem

First of all, let's make it clear: this problem is odd. In some cases, you will not be able to use TCP connections (HTTP, FTP, ...) at all and in others, you will be able to communicate with some hosts (very few).

When you have this problem, the dmesg's output is OK, logs are clean and ip addr will report normal status... and actually everything appears normal.

If you cannot browse any website, but you can ping some random hosts, chances are great that you're experiencing this problem: ping uses ICMP and is not affected by TCP problems.

You can try to use Wireshark. You might see successful UDP and ICMP communications but unsuccessful TCP communications (only to foreign hosts).

Ways of fixing it

Bad

To fix it the bad way, you can change the tcp_rmem value, on which Scale Factor calculation is based. Although it should work for most hosts, it is not guaranteed, especially for very distant ones.

# echo "4096 87380 174760" > /proc/sys/net/ipv4/tcp_rmem
Good

Simply disable Window Scaling. Since Window Scaling is a nice TCP feature, it may be uncomfortable to disable it, especially if you cannot fix the broken router. There are several ways to disable Window Scaling, and it seems that the most bulletproof way (which will work with most kernels) is to add the following line to /etc/sysctl.d/99-disable_window_scaling.conf (see also sysctl):

net.ipv4.tcp_window_scaling = 0
Best

This problem is caused by broken routers/firewalls, so let's change them. Some users have reported that the broken router was their very own DSL router.

More about it

This section is based on the LWN article TCP window scaling and broken routers and a Kernel Trap article: Window Scaling on the Internet.

There are also several relevant threads on the LKML.

Realtek no link / WOL problem

Users with Realtek 8168 8169 8101 8111(C) based NICs (cards / and on-board) may notice a problem where the NIC seems to be disabled on boot and has no Link light. This can usually be found on a dual boot system where Windows is also installed. It seems that using the offical Realtek drivers (dated anything after May 2007) under Windows is the cause. These newer drivers disable the Wake-On-LAN feature by disabling the NIC at Windows shutdown time, where it will remain disabled until the next time Windows boots. You will be able to notice if this problem is affecting you if the Link light remains off until Windows boots up; during Windows shutdown the Link light will switch off. Normal operation should be that the link light is always on as long as the system is on, even during POST. This problem will also affect other operating systems without newer drivers (eg. Live CDs). Here are a few fixes for this problem.

Enable the NIC directly in Linux

Follow #Enabling and disabling network interfaces to enable the interface.

Rollback/change Windows driver

You can roll back your Windows NIC driver to the Microsoft provided one (if available), or roll back/install an official Realtek driver pre-dating May 2007 (may be on the CD that came with your hardware).

Enable WOL in Windows driver

Probably the best and the fastest fix is to change this setting in the Windows driver. This way it should be fixed system-wide and not only under Arch (eg. live CDs, other operating systems). In Windows, under Device Manager, find your Realtek network adapter and double-click it. Under the "Advanced" tab, change "Wake-on-LAN after shutdown" to "Enable".

In Windows XP (example):

Right click my computer and choose "Properties"
--> "Hardware" tab
  --> Device Manager
    --> Network Adapters
      --> "double click" Realtek ...
        --> Advanced tab
          --> Wake-On-Lan After Shutdown
            --> Enable
Note: Newer Realtek Windows drivers (tested with Realtek 8111/8169 LAN Driver v5.708.1030.2008, dated 2009/01/22, available from GIGABYTE) may refer to this option slightly differently, like Shutdown Wake-On-LAN --> Enable. It seems that switching it to Disable has no effect (you will notice the Link light still turns off upon Windows shutdown). One rather dirty workaround is to boot to Windows and just reset the system (perform an ungraceful restart/shutdown) thus not giving the Windows driver a chance to disable LAN. The Link light will remain on and the LAN adapter will remain accessible after POST - that is until you boot back to Windows and shut it down properly again.

Newer Realtek Linux driver

Any newer driver for these Realtek cards can be found for Linux on the realtek site (untested but believed to also solve the problem).

Enable LAN Boot ROM in BIOS/CMOS

It appears that setting Integrated Peripherals --> Onboard LAN Boot ROM --> Enabled in BIOS/CMOS reactivates the Realtek LAN chip on system boot-up, despite the Windows driver disabling it on OS shutdown.

Note: This was tested several times on a GIGABYTE GA-G31M-ES2L motherboard, BIOS version F8 released on 2009/02/05.

No interface with Atheros chipsets

Users of some Atheros ethernet chips are reporting it does not work out-of-the-box (with installation media of February 2014). The working solution for this is to install backports-patchedAUR.

Broadcom BCM57780

This Broadcom chipset sometimes does not behave well unless you specify the order of the modules to be loaded. The modules are broadcom and tg3, the former needing to be loaded first.

These steps should help if your computer has this chipset:

  • Find your NIC in lspci output:
$ lspci | grep Ethernet
02:00.0 Ethernet controller: Broadcom Corporation NetLink BCM57780 Gigabit Ethernet PCIe (rev 01)
  • If your wired networking is not functioning in some way or another, try unplugging your cable then doing the following:
# modprobe -r tg3
# modprobe broadcom
# modprobe tg3
  • Plug your network cable in. If this solves your problems you can make this permanent by adding broadcom and tg3 (in this order) to the MODULES array in /etc/mkinitcpio.conf:
MODULES=".. broadcom tg3 .."
  • Rebuild the initramfs:
# mkinitcpio -p linux
  • Alternatively, you can create an /etc/modprobe.d/broadcom.conf:
softdep tg3 pre: broadcom
Note: These methods may work for other chipsets, such as BCM57760.

Realtek RTL8111/8168B

# lspci | grep Ethernet
03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 02)

The adapter should be recognized by the r8169 module. However, with some chip revisions the connection may go off and on all the time. The alternative r8168 can be found in the official repositories and should be used for a reliable connection in this case. Blacklist r8169, if r8168 is not automatically loaded by udev, see Kernel modules#Automatic module handling.

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: "some revisions", no proof the driver is the cause, and not e.g poorly configured DNS servers (Discuss in Talk:Network configuration#)

Another fault in the drivers for some revisions of this adapter is poor IPv6 support. IPv6#Disable functionality can be helpful if you encounter issues such as hanging webpages and slow speeds.

Gigabyte Motherboard with Realtek 8111/8168/8411

With motherboards such as the Gigabyte GA-990FXA-UD3, booting with IOMMU off (which can be the default) will cause the network interface to be unreliable, often failing to connect or connecting but allowing no throughput. This will apply not only to the onboard NIC, but any other pci-NIC you put in the box because the IOMMU setting affects the entire network interface on the board. Enabling IOMMU and booting with the install media will throw AMD I-10/xhci page faults for a second, but then boot normally, resulting in a fully functional onboard NIC (even with the r8169 module).

When configuring the boot process for your installation, add iommu=soft as a kernel parameter to eliminate the error messages on boot and restore USB3.0 functionality.

See also