[c-nsp] Multiple 802.1q subinterfaces with the same vlan under thesame physical interface

[Oliver Boehmer (oboehmer)]

luismi <> wrote on Monday, June 30, 2008 8:15 PM:

> Hi there,
> 
> I have a dude I could solve using a lab enviroment but for several
> reasons I don't have enought time at this momment, neither I have the
> correct equipment here.
> 
> I am thinking on collapse several routers configurations in new
> equipment, deploying subinterfaces with 802.1q and VRFs.
> 
> The situation is that for the same physical interface I would have
> several subinterfaces, working in the same vlan but diferent vrf, with
> also diferent ip addresses but all of them are in the same subnet.
> 
> The question is, is the router going to be enough clever to deliver
> the packet in the correct interface? Take note that the IP address
> use as destination in the incoming packet is not going to be ip
> address of the interface since the router and its vrfs.

This is not going to work. The router needs the vlan tag to associate
the appropriate (sub)interface with the packet, so the vlan tag has to
be unique on the interface (some platforms like the 6500 even ask for a
unique tag per system). VRF association comes later and is based on the
vrf configured on the (sub)interface.
So if you want to consolidate multiple vlan/.1q connections, you will
need to change vlan IDs in order to make them unique. 

	oli