[nsp] HSRP and VLANs

[Sam Stickland]

----- Original Message -----
From: "Marco Matarazzo"
To: "Sam Stickland"; "Jason Lixfeld"
Cc: <cisco-nsp at puck.nether.net>
Sent: Tuesday, December 16, 2003 2:26 PM
Subject: Re: [nsp] HSRP and VLANs


> > > As I understand it, you need at least 3 IPs to do HSRP for one subnet
> > > or VLAN.
> > Good point Jason! But I wonder how one can deliver a point to point
> > connection (I also have a couple of BGP downstreams) with a  /30, and
have
> > redundancy... there should been something we missed! At least I hope so!
> > Someone that can enlighten us?
>
> >HRSP is designed for first hop redunancy. For p2p connections you should
> >simply supply 2 seperate /30s and setup BGP to run over both of them.
>
> Yes yes, you're absolutely right! I was missing that point! But my
question
> is still open! :) How to provide redundancy to all my vlans without
growing
> each one's address space? (Wasting an ughly number of IPs!)

There isn't really any way to do it. There was some discussion on this list
earlier in the week about how you could configure the virtual IP address to
be the same as the physical IP address on one of the routers. I haven't
tried that myself (I'm not entirely convinced there aren't side effects, so
I want to do further investigation first), but that will mean you'll only
burn 1 extra IP address per subnet, rather than 2.

Alternatively, if by chance your customers have only a single connection
into a layer 3 capable switch (eg. 3550's) then you could place the default
gateway IP there (since it's already a single point of failure).

Sam