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12.07T2 has a BUG ?

Hello All,

I have a HUB-&-SPOKE setup (4 remote locations ie SPOKEs). Each site has a 2620 & running IOS 12.0(7)T2 (c2600-is-mz.120-7.T2.bin).

My issue is that... my Network Integrator implemented a ISDN BACKUP for my primary links using Dialer Profiles (using backup-delay & backup-inteface on primary interfaces). For past one month i am facing a problem that links (ISDN) are not picking UP as they r intended to do. I checked all configs, alongwith my NI and now they are saying.

IOS 12.0(7)T2 is the ROOT CAUSE for ISDN link failure....huh....

I want to know

1. Is there any ....channelized way i can go through TESTING MY BACKUP links (ISDN).


2. IS there a REAL PROBLEM with my IOS (c2600-is-mz.120-7.T2.bin).

hope someone can shed some light over it.


Vijayendra K. S.

  • Other Network Infrastructure Subjects

Re: 12.07T2 has a BUG ?

It might not be particularly a IOS / code issue, but I strongly recommend moving off 12.07T2 and going to the current 12.1 mainline GD release since that fixes quite a bit of issues since 12.0T code releases.

If the hub & spoke setup is frame relay then the backup interface may not kick in reliably due to the way frame relay works. When your frame becomes un-functional the interface may be up/up still. This is because the router may see the DLCIs still (LMI is working between your router and providers frame switch fine) -- but there may be a problem in the middle of carrier network(s) not visible to the edge frame switch your routers connect to. Also, does your carrrier send a A-bit when a PVC goes down?

Are you using point-to-point sub interfaces or multipoint? Point-to-point subs is better for backup.

In IOS version 12.0(4)T a new feature called Frame-Relay end to end keepalives (FREEK) was introduced that sends a keepalive end-to-end and if router doesn't receive so many keepalives in a certain period it will force the interface to a down state and the ISDN will come up. point-to-point sub interfaces are recommended w/FREEK.

When you're having trouble, find out the status of your frame relay interfaces (up/up, up/down, etc) on both sides.