[c-nsp] IS-IS hello packet size issues

[Alex]

Justin,
Have you tried "clns mtu" under interface?
Rgds
Alex

----- Original Message ----- 
From: "Justin Shore" <justin at justinshore.com>
To: "'Cisco-nsp'" <cisco-nsp at puck.nether.net>
Sent: Tuesday, May 08, 2007 3:10 PM
Subject: [c-nsp] IS-IS hello packet size issues


>I ran into another IS-IS problem this morning that stumped me.  I 
> migrated an ATM router to our new core.  In the process I took the 
> opportunity to try and get multi-area integrated IS-IS to work.  This 
> basically consisted of removing the related net from the main IS-IS 
> process (the current config is merging areas) and move that net to a new 
> IS-IS process.  Then I tried to enable IS-IS with the named tag on that 
> appropriate interface.  This prompted the following error:
> 
> %CLNS: Duplicate system ID configured in ip vrf <default> with router 
> isis null
> 
> I haven't been able to work around that issue.
> 
> I removed the new IS-IS process and added the net back to the original 
> process.  A few minutes later I received a page stating that a 
> completely unrelated edge router just went down.  The router turned out 
> to be up.  What happens was the IS-IS broke.  Through some debugging on 
> the edge router I determined that it was sending massive IS-IS IIHs 
> (9213 bytes).  The MTU on the physicals interfaces on both sides has 
> been set 9216.  The MPLS MTU has also been set to 9216.  MPLS and LDP 
> have both been enabled on the interfaces.  "No hello padding" was 
> configured on both sides.  That didn't help.  I enabled and disabled 
> hello padding on the edge router and they were all under 100 bytes.  I 
> check the packet size on the 7600s in the core.  I shutdown the 
> interfaces between the routers to kill IS-IS and then brought them back 
> online.  No luck.  Finally I rebooted the edge router.  IS-IS still 
> wasn't working the router came up.  This time however the IIHs were all 
> under 100bytes.  Then I checked the 7600 again.  At that point the 7600s 
> were sending 9213 bytes IIHs.  Rebooting them wasn't an option.
> 
> Has anyone seen this behavior before?
> 
> Thanks
>  Justin
> 
> 
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