http://www.linuxquestions.org – I've got a machine running Ubuntu Server that is on several VLANs. Each VLAN has its own subnet and the server has an address on each subnet. The switches are set to allow tagged traffic to the server for each VLAN that it is on. Switch ports ending with workstations are given untagged ports on whatever VLAN is appropriate. Workstations are given addresses on a subnet for each VLAN via DHCP. (HowTos)