Difference between revisions of "VLAN"

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m (Starting at boot: out of date)
(Starting at boot: netcfg -> netctl)
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===Starting at boot===
===Starting at boot===
{{Out of date|''netcfg'' has been superseded by [[netctl]]}}
You can use [[netctl]] for this purpose, see the self-explanatory example profiles in {{ic|/etc/netctl/examples/vlan-{dhcp,static} }}.
You can use the following parameters in [[netcfg]] profiles to have VLANs configured automatically:
# vlan specific part:
# general IP configuration:
Enable the daemon {{ic|netcfg@my-network}}. Read [[Daemons]] for more details.

Revision as of 20:18, 18 August 2013

Virtual LANs give you the ability to sub-divide a LAN. Linux can accept VLAN tagged traffic and presents each VLAN ID as a different network interface (eg: eth0.100 for VLAN ID 100) Template:Article summary start Template:Article summary text Template:Article summary heading Template:Article summary wiki Template:Article summary wiki Template:Article summary end


Previously Arch Linux used vconfigAUR to setup VLANs. This had been superseded by the ip command. Make sure you have iproute2 installed.

In the following examples, lets assume the interface is eth0, the assigned name is eth0.100 and the vlan id is 100.

Create the VLAN device

Add the VLAN with the following command:

# ip link add link eth0 name eth0.100 type vlan id 100

Run ip link to confirm that it has been created.

This interface behaves like a normal interface. All traffic routed to it will go through the master interface (in this example, eth0) but with a VLAN tag. Only VLAN aware devices can accept them if configured correctly else the traffic is dropped.

Using a name like eth0.100 is just convention and not enforced; you can alternatively use eth0_100 or something descriptive like IPTV

To see the VLAN ID on an interface, in case you used an unconventional name:

# ip -d link show eth0.100

The -d flag shows full details on an inteface.

Add an IP

Now add an IPv4 address to the just created vlan link, and activate the link:

# ip addr add brd dev eth0.100
# ip link set dev eth0.100 up

Turning down the device

To cleanly shutdown the setting before you remove the link, you can do:

# ip link set dev eth0.100 down

Removing the device

Removing a VLAN interface is significantly less convoluted

# ip link delete eth0.100

Starting at boot

You can use netctl for this purpose, see the self-explanatory example profiles in /etc/netctl/examples/vlan-{dhcp,static} .


udev renames the virtual devices

An annoyance is that udev may try to rename virtual devices as they are added, thus ignoring the name configured for them (in this case eth0.100).

For instance, if the following commands are issued:

# ip link add link eth0 name eth0.100 type vlan id 100
# ip link show 

This could generate the following output:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether aa:bb:cc:dd:ee:ff brd ff:ff:ff:ff:ff:ff
3: rename1@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state DOWN 
    link/ether aa:bb:cc:dd:ee:ff brd ff:ff:ff:ff:ff:ff

udev has ignored the configured virtual interface name eth0.100 and autonamed it rename1.

The solution is to edit /etc/udev/rules.d/network_persistent.rules and append DRIVERS=="?*" to the end of the physical interface's configuration line.

For example, for the interface aa:bb:cc:dd:ee:ff (eth0):

SUBSYSTEM=="net", ATTR{address}=="aa:bb:cc:dd:ee:ff", NAME="eth0", DRIVERS=="?*"

A reboot should mean that VLANs configure correctly with the names assigned to them.

See also