Configuring ISDN backup link

Unanswered Question
Jun 23rd, 2008

Hi everybody,

I have configured an ISDN BRI as backup link between two sites connected by a frame-relay link. One of routers in one-end was 2522 and was working fine. I relpaced this router by a 2611XM router recently, after replacement the backup ISDN link does not work.

The dialer interface has no been bound to BRI interface. I have two dialer profile: dialer1 and dialer2 to two different sites, diale 2 is bound to BRI0/0:1 but dialer1 is not. with old router (2522) both dialer interfaces are bound to BRI interfaces.

Thank you in advance for any advise.


I have this problem too.
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shillyar Mon, 06/23/2008 - 22:17

Please send in your confs and debug isdn q931 and debug ppp nego and debug ppp authe from both ends if possible.

Thx Steve

shillyar Mon, 06/23/2008 - 22:35

Hi Siamak,

On hostname r00569 your missing dialer-list 2

try adding that and see what happens

Thx Steve

Siamak.Mianji Mon, 06/23/2008 - 23:22

Hi Steve,

I added the dialer-list 2 but no difference.

#dialer-list 2 protocol ip permit



shillyar Mon, 06/23/2008 - 23:35

Hi Siamak,

Can you please run the q931 and ppp debugs so we can see what going on.

also sh isdn status shows L1 and L2 up and multiple frames established on both side id assume ?

Thx Steve

Siamak.Mianji Tue, 06/24/2008 - 01:02

Hi Steve,

Unfortunately I had to leave customer site, and I do not have access to that router until next Tuesday (1st of July). I will collect the debug information and will send them to you next Tuesday.

Many Thanks,


Richard Burts Tue, 07/01/2008 - 04:26


The information that you posted is helpful. I wonder if there are several issues involved. But the most important issue would seem to come from r00583 where the debug clearly shows an incoming call being rejected because the router is already busy with a different call. This router has a single BRI and 2 dialer interfaces. Dialer 1 is backing up the Frame Relay and Dialer 2 is not a backup and operates independently. At the time when you attempt to make a call for backup the Dialer 2 is already busy with a call.

I believe that if you check you will see that Dialer 2 is busy pretty much all the time because as it is configured EIGRP is active on the dialer interface (there is a network statement in EIGRP for and the dialer list/dialer group does not exclude EIGRP as interesting traffic. I see an access list 100 which may have been part of the dialer list at one point and would exclude EIGRP as interesting traffic. But the dialer list at this point is a simple protocol ip permit.




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