Create VLAN on Linux

# vconfig add
# ifconfig . netmask
# ifconfig . up

Eg:
# vconfig add eth0 5
# ifconfig eth0.5 192.168.1.5 netmask 255.255.255.0
# ifconfig eth0.5 up

View VLAN traffic
# cat /proc/net/vlan/eth0.5

You can have 2048 VLANS for one physical interface.