[nsp] Cisco Tag Switching Failure in IOS 12.0(17)ST3

From: Steven Godfrey (steven.godfrey@intechnology.co.uk)
Date: Wed Jan 09 2002 - 07:02:10 EST

I have come across a very serious problem in the IOS version we are running.

The bug results in a broken LSP between 2 adjacent routers, one of the two routers will show one or more of it's interfaces as not
operational for Tag Switching.

For some reason BGP sessions started to drop between certain routers, initial debugging showed all the correct routes and tag etc.

When you look at the tdp neighbours all seems to be ok, but when you look at the tag switching interfaces status it shows some as
The router on the other side of the faulty LSP show the tag status as Ok.

I have also looked at CEF etc and everything looks as it should.

I have left the current router in it's faulty state so I can continue to look at debug etc.

Attached is a text file with the output of the above commands.

I'm very keen to know if anyone has seen this bug and why a router should change the state of a tag switched interface to not
A shut no shut on the affected interface does clear the fault.

I have now seen this on 4 different occasions on the IOS version and Hardware shown in the attached file.



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