VLAN and Subinterfaces

[Nirav Modiya]

hello friends
 i want to know the procedure for creating VLAN and Subinterface on linux
box... actully i know about both vlan and subinterfaces as well as trunking
but i am not able to understand command in linux...

i want to know what the following commands do exectly...

vconfig add eth0 3
ifconfig eth0:3
actully i want to know the difference between this two...

and let say i have two subinterfaces created on 3 and 4 ...and my linux box
is connected with cisco switch with trunk having vlan 3 and 4...
now i want to establish communication between host on vlan 3 and host on
vlan 4 using linux box ... my cisco switch is layer-2 switch...

subinterface 3 on linux box and host in vlan 3 which connected with the
switch both are in same subnet...(192.168.1.0 )
subinterface4 on linux box and host in vlan 4 which connected with the
switch both are in same subnet...(192.168.2.0 )

now i have to enable intervlan routing between subinterface3 and
subinterface4... to full fill my requirement...or routing between this
subinterface will be enable by default...

with regards
Nirav Modiya