[c-nsp] How to bring one link down if another related link goes down

[Ziv Leyes]

Or, if your equipment supports it, use ip sla and track based routing.
I use this solution for a couple of tunnels, here's an example:

======================================
ip sla monitor 1
 type echo protocol ipIcmpEcho 1.1.1.1
!
ip sla monitor schedule 1 life forever start-time now
!
track 1 rtr 1 reachability
!

ip sla monitor 2
 type echo protocol ipIcmpEcho 2.2.2.2
!
ip sla monitor schedule 2 life forever start-time now
!
track 2 rtr 2 reachability
!

ip route 10.0.0.0 255.255.255.0 1.1.1.1 100 name track 1
ip route 10.0.0.0 255.255.255.0 2.2.2.2 200 name track 2
======================================

As long as 1.1.1.1 is available, it's routing will be valid because the smaller administrative distance, if not, then the second one will become active.
In any case, you'll always see only one routing line in table.

Hope this helps,
Ziv



-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Mikael Abrahamsson
Sent: Tuesday, September 28, 2010 7:52 AM
To: John Neiberger
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] How to bring one link down if another related link goes down

On Mon, 27 Sep 2010, John Neiberger wrote:

> That may be the best idea I've seen. It wouldn't even be necessary for 
> it to bring the links back up automatically. If one link goes down, 
> we're going to need to do a lot of careful troubleshooting before we 
> bring it up, so a manual restoration process would be best.

I recommend changing the metric of the routing protocol of the link instead of shutting it down. Set it to a very high value indicating the link is "a last resort". Do it at both ends.

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se
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