Use of dot1q subinterfaces

First Team Netops · ‎03-12-2009

Can anyone tell me the benifit of using two dot1q subinterfaces when going from a 3560 switch to a 3725 router rather than using two different physical interfaces?

Thanks.

Nicholas Matthews · ‎03-12-2009

Hi Jim,

This is helpful if you have a shortage of interfaces. If you have two interfaces and you know you're not going to need spares, then you can do either way and they are equivalent.

They are more often used in situations that:

1) You have more vlans than ports

2) You want to leave the other port to do other things, or for expansion.

They're really quite simple, and once you get used to them you may find them easier. Because if in the future you want to add another VLAN/IP to the router, it's as simple as adding another subinterface and there are no troubles.

hth,

nick