Difference between revisions of "Network configuration (Português)"
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[[zh-CN:Network Configuration]] | [[zh-CN:Network Configuration]] | ||
{{Article summary start}} | {{Article summary start}} | ||
− | {{Article summary text| | + | {{Article summary text|Um guia simples de configuração e resolução de problemas de rede.}} |
{{Article summary heading|Overview}} | {{Article summary heading|Overview}} | ||
{{Article summary text|{{Networking overview}}}} | {{Article summary text|{{Networking overview}}}} | ||
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Veja {{ic|man 5 hostname}} e {{ic|man 1 hostnamectl}} para maiores detalhes. | Veja {{ic|man 5 hostname}} e {{ic|man 1 hostnamectl}} para maiores detalhes. | ||
− | |||
{{Note| | {{Note| | ||
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Caso o udev não detecte ou não carregue o módulo de forma apropriada e automaticamente durante o boot, veja a página [[Kernel modules#Loading]]. | Caso o udev não detecte ou não carregue o módulo de forma apropriada e automaticamente durante o boot, veja a página [[Kernel modules#Loading]]. | ||
− | == | + | == Interfaces de Rede == |
− | === | + | === Nomes de dispositivos === |
− | + | Para placas-mãe que possuem interfaces de rede embutidas, é importante ter um nome de dispositivo fixo. Grande parte dos problemas são causados por nomes de dispositivos que mudam. | |
− | [[Udev]] | + | O [[Udev]] é o responsavel por qual nome um dispositivo deve receber. O systemd v197 introduziu os [http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames nomes de interface previsíveis], que automaticamente atribuem nomes estáticos a dispositivos de rede. Interfaces são prefixadas como en (ethernet), wl (WLAN), ou ww (WWAN) seguido por um identificados, criando uma entrada similar a {{ic|enp0s25}}. |
− | + | Este comportamento pode ser desabilitado com o segunite link simbólico: | |
# ln -s /dev/null /etc/udev/rules.d/80-net-name-slot.rules | # ln -s /dev/null /etc/udev/rules.d/80-net-name-slot.rules | ||
− | + | Usuários atualizando de uma versão mais antiga do systemd terão arquivos de regras criados automaticamente em branco. Caso você queira usar os nomes persistentes, apenas delete tal arquivo. | |
− | {{Tip| | + | {{Tip|Você pode rodar um {{ic|ip link}} ou {{ic|ls /sys/class/net}} para listar todas as interfaces.}} |
− | ==== | + | ==== Alterando o nome de um dispositivo ==== |
− | + | ||
+ | Você pode alterar o nome de um dispositivo definindo o nome em uma regra do udev. Exemplo: | ||
{{hc|/etc/udev/rules.d/10-network.rules|2= | {{hc|/etc/udev/rules.d/10-network.rules|2= | ||
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 | + | Alguns detalhes devem ser ressaltados: |
+ | * Para obter o endereço MAC de cada interface, utilize o comando {{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>}} --> | ||
+ | * Certifique-se de utilizar valores em caixa baixa para valores hexadecimais em regras do udev. Ele não gosta de caixa alta. | ||
+ | {{Note|Quando escolher nomes estáticos '''nomes no formato "eth''X''" and "wlan''X''" devem ser evitados''', pois podem causar race conditions entre o kernel e o udev durante o boot. É melhor utilizar nomes que não são os padrões do kernel como: {{ic|net0}}, {{ic|net1}}, {{ic|wifi0}}, {{ic|wifi1}}. Para maiores detalhes, veja a documentação do [http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames systemd].}} | ||
− | + | === Alterando MTU e tamanho da fila === | |
− | |||
− | |||
− | + | Você pode alterar o MTU de um dispositivo através de uma regra do udev. Exemplo: | |
− | |||
{{hc|/etc/udev/rules.d/10-network.rules|2= | {{hc|/etc/udev/rules.d/10-network.rules|2= | ||
ACTION=="add", SUBSYSTEM=="net", KERNEL=="wl*", ATTR{mtu}="1480", ATTR{tx_queue_len}="2000"}} | ACTION=="add", SUBSYSTEM=="net", KERNEL=="wl*", ATTR{mtu}="1480", ATTR{tx_queue_len}="2000"}} | ||
− | === | + | === Descobrir nome dos dispositivos atuais === |
− | + | Os nomes dos dispositivos em execução podem ser obtidos através do sysfs | |
{{hc|$ ls /sys/class/net| | {{hc|$ ls /sys/class/net| | ||
Line 143: | Line 143: | ||
=== Enabling and disabling network interfaces === | === Enabling and disabling network interfaces === | ||
+ | === Ativando e desabilitando interfaces de rede === | ||
− | + | Você pode ativar e desabilitar interfaces de rede através dos comandos: | |
# ip link set eth0 up | # ip link set eth0 up | ||
# ip link set eth0 down | # ip link set eth0 down | ||
− | + | Prova real: | |
{{hc|$ ip link show dev eth0| | {{hc|$ ip link show dev eth0| | ||
Line 155: | Line 156: | ||
[...]}} | [...]}} | ||
− | == | + | == Configurando endereços IP == |
+ | |||
+ | Você possui duas opções: Endereços dinâmicos através de [http://pt.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol DHCP] ou um endereço "estático". | ||
− | + | === Endereço IP dinâmico === | |
− | |||
− | === | ||
− | ==== | + | ==== Execução manual do serviço(daemon) DHCP ==== |
− | + | Note que {{ic|dhcpcd}} não é {{ic|dhcpd}}. | |
{{hc|# dhcpcd eth0| | {{hc|# dhcpcd eth0| | ||
Line 171: | Line 172: | ||
dhcpcd: eth0: leased 192.168.1.70 for 86400 seconds}} | dhcpcd: eth0: leased 192.168.1.70 for 86400 seconds}} | ||
− | + | Através do comando, {{ic|ip addr show dev eth0}} você verificará o endereço obtido. | |
− | + | Em alguns cenários, o comando {{ic|dhclient}} do pacote {{Pkg|dhclient}} funcionará e o {{ic|dhcpcd}} falhará. | |
− | ==== | + | ==== DHCP durante o boot ==== |
− | + | Se você deseja apenas usar o DHCP em sua coenxão cabeada, você pode usar o serviço {{ic|dhcpcd@.service}} provido pelo pacote {Pkg|dhcpcd}}, | |
− | + | Para iniciar o DHCP na interface {{ic|eth0}}: | |
# systemctl start dhcpcd@eth0 | # systemctl start dhcpcd@eth0 | ||
− | + | Você pode habilitar o serviço para iniciar no boot do sistema com o comando: | |
+ | |||
# systemctl enable dhcpcd@eth0 | # systemctl enable dhcpcd@eth0 | ||
− | + | Caso o serviço dhcpd inicie antes do módulo da interface de rede ser carregado({{bug|30235}}), adicione sua interface de rede ao arquivo {{ic|/etc/modules-load.d/*.conf}}. Por exemplo, se o módulo da Realtek {{ic|r8169}} precisa ser carregado crie o arquivo: | |
{{hc|/etc/modules-load.d/realtek.conf| | {{hc|/etc/modules-load.d/realtek.conf| | ||
r8169}} | r8169}} | ||
+ | |||
+ | {{Tip|Para descobrir quais módulos são utilizados por uma placa de rede, utilize o comando {{ic|lspci -k}}.}} | ||
+ | |||
{{Tip|To find out which modules are used by your network card, use {{ic|lspci -k}}.}} | {{Tip|To find out which modules are used by your network card, use {{ic|lspci -k}}.}} | ||
− | + | Se você utiliza DHCP e '''não''' deseja ter o DNS configurado automaticamente cada vez que a rede for iniciada, adicione o seguinte conteúdo na última sessão do arquivo {{ic|dhcpcd.conf}}: | |
{{hc|/etc/dhcpcd.conf| | {{hc|/etc/dhcpcd.conf| | ||
nohook resolv.conf}} | nohook resolv.conf}} | ||
− | + | Para previnir que o {{ic|dhcpcd}} adicione nomes de domínio ao {{ic|/etc/resolv.conf}}, use a opção {{ic|nooption}}: | |
{{hc|/etc/dhcpcd.conf| | {{hc|/etc/dhcpcd.conf| | ||
nooption domain_name_servers}} | nooption domain_name_servers}} | ||
− | + | Assim, você poderá editar o arquivo {{ic|/etc/resolv.conf}} com suas próprias configurações de DNS. | |
− | + | Você pode usar o pacote {{Pkg|openresolv}} caso diferentes processos desejam controlar o arquivo {{ic|/etc/resolv.conf}} (por exemplo, {{Pkg|dhcpcd}} e um cliente de VPN). Nenhuma configuração adicional para o {{Pkg|dhcpcd}} é necessária para se adequar ao {{Pkg|openresolv}}. | |
=== Static IP address === | === Static IP address === |
Revision as of 18:12, 28 August 2013
zh-CN:Network Configuration Template:Article summary start Template:Article summary text Template:Article summary heading Template:Article summary text Template:Article summary heading Template:Article summary wiki Template:Article summary wiki Template:Article summary wiki Template:Article summary end
Esta página explica como configurar uma conexão cabeada. Se você deseja configurar uma rede wireless/sem fio veja a página Configuração de Redes Sem Fio.
Contents
- 1 Verificando a conexão
- 2 Configurando um hostname
- 3 Drivers de dispositivos
- 4 Interfaces de Rede
- 5 Configurando endereços IP
- 6 Load configuration
- 7 Additional settings
- 8 Troubleshooting
- 8.1 Swapping computers on the cable modem
- 8.2 The TCP window scaling problem
- 8.3 Realtek no link / WOL problem
- 8.4 DLink G604T/DLink G502T DNS problem
- 8.5 Check DHCP problem by releasing IP first
- 8.6 No eth0 with Atheros AR8161
- 8.7 No eth0 with Atheros AR9485
- 8.8 No carrier / no connection after suspend
- 8.9 PC Pingable by IP but not by hostname?
- 8.10 Broadcom BCM57780
Verificando a conexão
ping: icmp open socket: Operation not permitted
quando executar o comando ping, tente reinstalar o pacote iputils
.Muitas vezes, o procedimento básico de instalação cria uma configuração de rede cabeada. Para verificar se há configuração, utilize o seguinte comando:
-c 3
chama 3 vezes a ação de envio de pacotes icmp. Veja man ping
para maiores informações.$ ping -c 3 www.google.com
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 --- 3 packets transmitted, 3 received, 0% packet loss, time 1999ms rtt min/avg/max/mdev = 298.107/373.642/437.202/57.415 ms
Caso funcione, você precisará apenas personalizar algumas das opções abaixo.
Se o comando acima reclamar de unknown hosts(host desconhecido), significa que seu computador não pôde resolver nomes de domínios. Pode ser relacionado ao seu provedor de internet ou gateway/roteador. Tente pingar um endereço IP para provar que sua máquina possui acesso a internet.
$ ping -c 3 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 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 --- 8.8.8.8 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2002ms rtt min/avg/max/mdev = 52.975/65.375/72.543/8.803 ms
8.8.8.8
é um endereço ip estático de fácil memorização. É o endereço do DNS primário do Google, considerado uma fonte confiável para testes e geralmente não bloqueado por sistemas de filtro de conteúdo ou proxies.Caso você consiga pingar este endereço, pode adicioná-lo ao arquivo /etc/resolv.conf
com a palavra nameserver na frente como solução de dns.
Configurando um hostname
Um A hostname é um endereço único criado para identificar um computador em uma rede. É configurado no arquivo /etc/hostname
. Este arquivo pode conter o domínio do sistema, se houver. Para configurar um hostname, execute:
# hostnamectl set-hostname meunome
Este comando colocará a informação meunome no arquivo /etc/hostname
.
Veja man 5 hostname
e man 1 hostnamectl
para maiores detalhes.
hostnamectl
suporta FQDNs- Você não precisa mais editar o arquivo
/etc/hosts
, pois o systemd proverá a resolução de nomes, e é instalado por padrão no sistema.
Para alterar o hostname temporariamente(até o próximo restart), utilize o comando hostname
do pacote inetutils:
# hostname meunome
Drivers de dispositivos
Verifique o estado do seu driver
O udev deverá detectar sua interface de rede(NIC) e carregará automaticamente o módulo necessário. Busque pela entrada "Ethernet controller"(ou similar) no resultado do comando lspci -v
. Este comando dirá qual módulo do kernel é necessário para o funcionamento do dispositivo. Por exemplo:
$ lspci -v
02:00.0 Ethernet controller: Attansic Technology Corp. L1 Gigabit Ethernet Adapter (rev b0) ... Kernel driver in use: atl1 Kernel modules: atl1
Após, veja se o driver foi carregado através de um dmesg | grep module_name
. Exemplo:
$ dmesg | grep atl1 ... atl1 0000:02:00.0: eth0 link is up 100 Mbps full duplex
Pule para a próxima sessão caso o driver tenha sido carregado com sucesso. Caso contrário, você precisará descobrir qual é o módulo necessário para o seu modelo de interface de rede em específico.
Carregando o driver do dispositivo
Busque na internet(google) pelo modelo de sua placa e descubra qual o chipset. Algumas placas mais comuns utilizam o chipset da Realtek 8139too
, ou sis900
da SiS. Assim que descobrir qual módulo deve usar, tente carregar o módulo manualmente. Caso você esbarre com algum erro dizendo que o módulo não foi encontrado, é possível que o driver não foi incluído no kernel do Arch Linux. Tente procurar no AUR pelo nome do módulo.
Caso o udev não detecte ou não carregue o módulo de forma apropriada e automaticamente durante o boot, veja a página Kernel modules#Loading.
Interfaces de Rede
Nomes de dispositivos
Para placas-mãe que possuem interfaces de rede embutidas, é importante ter um nome de dispositivo fixo. Grande parte dos problemas são causados por nomes de dispositivos que mudam.
O Udev é o responsavel por qual nome um dispositivo deve receber. O systemd v197 introduziu os nomes de interface previsíveis, que automaticamente atribuem nomes estáticos a dispositivos de rede. Interfaces são prefixadas como en (ethernet), wl (WLAN), ou ww (WWAN) seguido por um identificados, criando uma entrada similar a enp0s25
.
Este comportamento pode ser desabilitado com o segunite link simbólico:
# ln -s /dev/null /etc/udev/rules.d/80-net-name-slot.rules
Usuários atualizando de uma versão mais antiga do systemd terão arquivos de regras criados automaticamente em branco. Caso você queira usar os nomes persistentes, apenas delete tal arquivo.
ip link
ou ls /sys/class/net
para listar todas as interfaces.Alterando o nome de um dispositivo
Você pode alterar o nome de um dispositivo definindo o nome em uma regra do udev. Exemplo:
/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"
Alguns detalhes devem ser ressaltados:
- Para obter o endereço MAC de cada interface, utilize o comando
cat /sys/class/net/device-name/address
- Certifique-se de utilizar valores em caixa baixa para valores hexadecimais em regras do udev. Ele não gosta de caixa alta.
net0
, net1
, wifi0
, wifi1
. Para maiores detalhes, veja a documentação do systemd.Alterando MTU e tamanho da fila
Você pode alterar o MTU de um dispositivo através de uma regra do udev. Exemplo:
/etc/udev/rules.d/10-network.rules
ACTION=="add", SUBSYSTEM=="net", KERNEL=="wl*", ATTR{mtu}="1480", ATTR{tx_queue_len}="2000"
Descobrir nome dos dispositivos atuais
Os nomes dos dispositivos em execução podem ser obtidos através do sysfs
$ ls /sys/class/net
lo eth0 eth1 firewire0
Enabling and disabling network interfaces
Ativando e desabilitando interfaces de rede
Você pode ativar e desabilitar interfaces de rede através dos comandos:
# ip link set eth0 up # ip link set eth0 down
Prova real:
$ 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 [...]
Configurando endereços IP
Você possui duas opções: Endereços dinâmicos através de DHCP ou um endereço "estático".
Endereço IP dinâmico
Execução manual do serviço(daemon) DHCP
Note que dhcpcd
não é dhcpd
.
# dhcpcd eth0
dhcpcd: version 5.1.1 starting dhcpcd: eth0: broadcasting for a lease ... dhcpcd: eth0: leased 192.168.1.70 for 86400 seconds
Através do comando, ip addr show dev eth0
você verificará o endereço obtido.
Em alguns cenários, o comando dhclient
do pacote dhclient funcionará e o dhcpcd
falhará.
DHCP durante o boot
Se você deseja apenas usar o DHCP em sua coenxão cabeada, você pode usar o serviço dhcpcd@.service
provido pelo pacote {Pkg|dhcpcd}},
Para iniciar o DHCP na interface eth0
:
# systemctl start dhcpcd@eth0
Você pode habilitar o serviço para iniciar no boot do sistema com o comando:
# systemctl enable dhcpcd@eth0
Caso o serviço dhcpd inicie antes do módulo da interface de rede ser carregado(FS#30235), adicione sua interface de rede ao arquivo /etc/modules-load.d/*.conf
. Por exemplo, se o módulo da Realtek r8169
precisa ser carregado crie o arquivo:
/etc/modules-load.d/realtek.conf
r8169
lspci -k
.
lspci -k
.Se você utiliza DHCP e não deseja ter o DNS configurado automaticamente cada vez que a rede for iniciada, adicione o seguinte conteúdo na última sessão do arquivo dhcpcd.conf
:
/etc/dhcpcd.conf
nohook resolv.conf
Para previnir que o dhcpcd
adicione nomes de domínio ao /etc/resolv.conf
, use a opção nooption
:
/etc/dhcpcd.conf
nooption domain_name_servers
Assim, você poderá editar o arquivo /etc/resolv.conf
com suas próprias configurações de DNS.
Você pode usar o pacote openresolv caso diferentes processos desejam controlar o arquivo /etc/resolv.conf
(por exemplo, dhcpcd e um cliente de VPN). Nenhuma configuração adicional para o dhcpcd é necessária para se adequar ao openresolv.
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.
You need:
- Static IP address
- Subnet mask
- Broadcast address
- Gateway's IP address
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.
Manual assignment
You can assign a static IP address in the console:
# ip addr add <IP address>/<subnet mask> dev <interface>
For example:
# ip addr add 192.168.1.2/24 dev eth0
For more options, see man ip
.
Add your gateway like so:
# ip route add default via <default gateway IP address>
For example:
# ip route add default via 192.168.1.1
If you the get the error "No such process", it means you have to run ip link set dev eth0 up
as root.
Manual connection at boot using systemd
First create configuration file for the systemd service, replace <interface>
with proper interface name:
/etc/conf.d/network@<interface>
address=192.168.0.15 netmask=24 broadcast=192.168.0.255 gateway=192.168.0.1
Create a systemd unit file:
/etc/systemd/system/network@.service
[Unit] Description=Network connectivity (%i) Wants=network.target Before=network.target BindsTo=sys-subsystem-net-devices-%i.device After=sys-subsystem-net-devices-%i.device [Service] Type=oneshot RemainAfterExit=yes EnvironmentFile=/etc/conf.d/network@%i ExecStart=/usr/bin/ip link set dev %i up ExecStart=/usr/bin/ip addr add ${address}/${netmask} broadcast ${broadcast} dev %i ExecStart=/usr/bin/ip route add default via ${gateway} ExecStop=/usr/bin/ip addr flush dev %i ExecStop=/usr/bin/ip link set dev %i down [Install] WantedBy=multi-user.target
Enable the unit and start it, passing the name of the interface:
# systemctl enable network@eth0.service # systemctl start network@eth0.service
Calculating addresses
You can use ipcalc
provided by the 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.
$ 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
Load configuration
To test your settings either reboot the computer or reload the relevant systemd services:
# systemctl restart dhcpcd@eth0
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
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
.
netctl-ifplugd@.service
, otherwise you can use ifplugd@.service
from ifplugd package. Use for example systemctl enable ifplugd@eth0.service
.Bonding or LAG
See netctl#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
You will need netctl from the Official Repositories.
Prepare the configuration:
/etc/netctl/mynetwork
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')
Then simply execute:
$ netctl start mynetwork
Change MAC/hardware address
See MAC Address Spoofing.
See Internet Share.
Router Configuration
See Router.
Troubleshooting
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.
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).
How to fix it (The bad way)
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
How to fix it (The good way)
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.conf
(see also sysctl)
net.ipv4.tcp_window_scaling = 0
How to fix it (The best way)
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 operative systems without newer drivers (eg. Live CDs). Here are a few fixes for this problem:
Method 1 - 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).
Method 2 - 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.
In Windows XP (example) Right click my computer --> Hardware tab --> Device Manager --> Network Adapters --> "double click" Realtek ... --> Advanced tab --> Wake-On-Lan After Shutdown --> Enable
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
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
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.
This was tested successfully multiple times with GIGABYTE system board GA-G31M-ES2L with BIOS version F8 released on 2009/02/05. YMMV.
DLink G604T/DLink G502T DNS problem
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
How to diagnose the problem
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 links
through the live CD.
Firstly, enable wget for pacman (since it gives us info about pacman when it is downloading packages)
Open /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
While you are editing /etc/pacman.conf
, check the default mirror that pacman uses to download packages.
Now open up the default mirror in an Internet browser to see if the mirror actually works. If it does work, then do 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),
ftp://mirror.pacific.net.au/linux/archlinux/extra/os/i686/extra.db.tar.gz => '/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 /etc/resolv.conf
.
How to fix it
Basically what we need to do is to manually add the DNS servers to our /etc/resolv.conf
file. The problem is that DHCP automatically deletes and replaces this file on boot, so we need to edit /etc/conf.d/dhcpcd
and change the flags to stop DHCP from doing this.
When you open /etc/conf.d/dhcpcd
, you should see something close to the following:
DHCPCD_ARGS="-t 30 -h $HOSTNAME"
Add the -R
flag to the arguments, e.g.,
DHCPCD_ARGS="-R -t 30 -h $HOSTNAME"
-R
flag has been deprecated. Please see the #For DHCP assigned IP address section for information on how to use a custom /etc/resolv.conf
file.Save and close the file; now open /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.
For example, /etc/resolv.conf
should look something along the lines of:
nameserver 10.1.1.1
If my primary DNS server is 211.29.132.12, then change /etc/resolv.conf
to:
nameserver 211.29.132.12 nameserver 10.1.1.1
Now restart the network daemon by running systemctl restart dhcpcd@<interface>
and do 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 compat-wireless (that has become 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 mailing listand alx pagefor latest working solution for alx.
The driver must be built and installed after every kernel change.
Alternatively you can use the AUR package for 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 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. 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"
Don't forget to substitute the address again.
PC Pingable by IP but not by hostname?
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:
systemctl start smbd.service systemctl start nmbd.service
And that makes the computer available by name on the network.
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:
$ 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 (as root):
# modprobe -r tg3 # modprobe broadcom # modprobe tg3
Now plug you 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 .."
Then rebuild the initramfs:
# mkinitcpio -p linux