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

[luismi]

My conclusion is that in the scenario I am using the problem is that it
won't be possible to configure a router with several subinterfaces in
the same vlan under the same physical interface due an issue with the
MAC address and the switches side.

And yes, At the moment I am just trying to consolidate the router side,
reduce the management efforts, point of failures... since we go for just
2 routers in HSRP with vlans and VRF instead of a 4 routers (2 x HSRP).

Thanks for all the comments.


El mié, 02-07-2008 a las 11:38 +0200, Oliver Boehmer (oboehmer)
escribió:
> luismi <mailto:asturluismi at gmail.com> wrote on Wednesday, July 02, 2008 11:23 AM:
> 
> > What I was thinking in assign different subinterfaces (from different
> > physical interfaces) to the same vlan in the same chassis.
> > 
> > I think that the router will be able to manage that configuration, for
> > example: fa0/0.1 and fa1/0.1 working in different vrfs but in the same
> > vlan, with different IP address from the same subnet.
> > 
> > Is that correct?
> 
> yes, this will work on most platforms. The 6500/7600 uses system-wide vlans (with a few exceptions), so this won't work there..
> Tom's comment on the (possibly connected) switched infrastructure still applies, but if you are "only" consolidating the router part, it should work.
> 
> 	oli
> 
> 
> > 
> > El mié, 02-07-2008 a las 08:22 +0200, Oliver Boehmer (oboehmer)
> > escribió:
> >> 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