Setting up VLANs/trunking on a Debian machine

1. Install VLAN utilities:
   • apt-get update
   • apt-get install vlan
2. Edit /etc/network/interfaces and add the line like:
   • auto ethX.Y
   • where X is the physical eth device number and Y is the VLAN number
3. Add an IP address, netmask, broadcast address, etc. like any other interface, e.g.
   • auto eth0.49
   • iface eth0.49 inet static
   • address 129.97.49.9
   • netmask 255.255.255.0
   • broadcast 129.97.49.255
4. Bring the interface up:
   • ifup eth0.49
5. You might get a warning about it being unable to open /proc/net/vlan/config, that's because vconfig tries to access proc before the kernel autoloads the module. Verify that the interface is working properly by doing cat /proc/net/vlan/config after. You should see something like:
   • eth0.49      | 49 | eth0
6. Instead of ethX.Y, you can also use the format vlan# where # is the vlan number. In this case, a line also must be present in the iface declaration that links the vlan to a device, e.g. vlan_raw_device eth0

Notes

• ifdown [interface] does not remove the vlan from the vlan tables, to remove it do vconfig rem [interface] where interface is the VLAN interface (e.g. eth0.49 or vlan49), not the actual eth device