[c-nsp] default route behavoir

Scott Granados gsgranados at comcast.net
Tue Dec 11 18:16:52 EST 2007


I forget if it's supported as well but you could use object tracking in the 
IP SLA features to track a far end device for whether it's reached or not 
and flop routes in the event one is not reached.  (in place of an IGP)  This 
works great for DSL backup, something similar should work here.




----- Original Message ----- 
From: "Matlock, Kenneth L" <MatlockK at exempla.org>
To: <cisco-nsp at puck.nether.net>
Sent: Tuesday, December 11, 2007 3:10 PM
Subject: Re: [c-nsp] default route behavoir


> Currently both routes are equal cost, so the first packet (or flow,
> can't remember which off the top of my head) takes the first route, and
> the next packet (or flow) takes the 2nd route, and the 3rd packet (or
> flow) takes the 1st route, etc.
>
> In order to do it, you can change the metric on the non-preferred route
> so it's only used if the other route is unavailable.
>
> ip route 0.0.0.0 0.0.0.0 10.50.6.2
> ip route 0.0.0.0 0.0.0.0 10.50.5.24 2
>
> now, keep in mind that the switch will only determine that 10.50.6.2 is
> down if the interface that 10.50.6.2 is connected changes state to down.
> If the state doesn't change, that route's still valid even if 10.50.6.2
> is no longer responding.
>
> In order to solve that, you need to run a dynamic protocol between this
> 3560 and the upstream routers/switches. (I don't know off the top of my
> head if/what the 3560 supports).
>
>
> Ken Matlock
> Network Analyst
> (303) 467-4671
> matlockk at exempla.org
>
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Dan Letkeman
> Sent: Tuesday, December 11, 2007 4:01 PM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] default route behavoir
>
> Hello,
>
> I'm unsure how the default route behavior is supposed to be on a 3560
> switch.  I have a remote office that is connected with two wireless
> links to
> a main building.  Right now I have this in my configuration for
> redundancy,
> but it is using both links and just randomly taking either one.
>
> ip route 0.0.0.0 0.0.0.0 10.50.6.2
> ip route 0.0.0.0 0.0.0.0 10.50.5.24
>
> Is there a way to tell the switch to only use 10.50.6.2 and not use
> 10.50.5.24 unless 10.50.6.2 is down?
>
> Thanks,
> Dan.
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