policy based routing with isdn backup

Unanswered Question
Apr 2nd, 2007


I have successfully configured PBR on the 2621 XM router. The purpose is to route mail traffic to the LL interface, and all other traffic to the frame realy interface. It all works and looks ok.

The mail ISP supports isdn connections as well, so I want to configure my serial (LL) interface to switch to the BRI when the link goes down.

The problem is that I can't properly set-up the PBR. I tried with this:

route-map mail-ISP permit

match ip address 111

set default interface Serial0/0 Dialer1

but this wont' work. When the s0/0 is down, nothing happens. I wonder if this is the right configuration at all? I didn't find what this command truly do:

set default interface IF1 IF2...

What is the proper usage? Will it ever go to IF2?

Or I am on the wrong track in the first place.. I even tried with "backup interface" command, but again with no luck. When s0/0 goes down, dialer1 goes up, but there are no placed active calls(!) Again, no calls, but dialer1 is up... Strange...

Can someone please give me a hint. I can post more details/configs/debugs if needed.

Thanks in advance.

I have this problem too.
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m-haddad Mon, 04/02/2007 - 12:09


Did you try using next hop instead of interface?


Bojan Zivancevic Mon, 04/02/2007 - 13:00

As a matter of fact, I did not. How can I put the next hop when I'm dialing into ISP's network? I don't know the next hop ip address in advance?

Serial0/0 interface is working fine, PBR is doing the job (with the 'interface' syntax.) But I can't put the isdn interface into function.


m-haddad Mon, 04/02/2007 - 13:09

Which IOS version are you running? Can you paste your ACL please?


Bojan Zivancevic Tue, 04/10/2007 - 05:06

Sorry for the late answer, I was sick for a few days.

Here's the IOS version:

C2600-IPBASE-M, Version 12.3(6f), RELEASE SOFTWARE (fc1)

Here's the acl:

access-list 111 permit ip host any

This is the only address for the route map. Anything that goes from it, should be routed through serial0/0, and if that IF isn't working it should go through dialer1.

Here's my DDR config:

access-list 101 permit ip host any

dialer-list 1 protocol ip list 101

interface Dialer1

dialer-group 1


It's very basic configuration. I don't see any problems whatsoever. And when I turn on the policy-map debug, I can clearly see that the traffic is routed to dialer1, but nothing happens - no calls at all.



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