Add module '8021q' to /etc/modules
Install package 'vlan'
iface vlan1 inet6 static
address 2000::1:202:b3ff:feda:ec80
netmask 64
mtu 1496 # important for 3c59x that does not support vlan
# needs to be added to inet6 interface, otherwise mtu for ipv6 is set to 1500!
vlan_raw_device eth0
http://www.linuxjournal.com/article/7268
http://www.candelatech.com/~greear/vlan/howto.html
http://www.candelatech.com/~greear/vlan.html