Re: [nsp] ICMP Unreachable and CEF

From: Steven W. Raymond (steven_raymond@eli.net)
Date: Thu Jan 24 2002 - 11:36:20 EST


Have experienced this same problem also and working with Cisco, was
provided the following bug id: CSCdj55180
Output is very terse. Is there anyone here from Cisco that can
elaborate on an expected fix timeline?
I believe that one workaround (somewhat lame) is to instead route to
another unused interface which is up/up but without an IP address. This
will generate an ICMP unreachable due to the unnumbered interface. Be
sure to turn off cef on that interface. It was explained to me that if
cef is turned on, then the RSP (which generates the ICMP unreachable)
never sees the packet.
The problem is not observed on the 12000 platform with the exact same
code version 12.0(14)S5.
Regards

Elijah Kagan wrote:
>
> I always thought that when a router forwards packets to Null0 it also
> generates ICMP Unreachable message to indicate this event. It seems that
> this is not the case on routers running CEF. I checked this on several
> platforms: 7500, 7200 and 3600. Whenever CEF is turned off I see those
> unreachables pouring in, with CEF on - nothing.
>
> Is this the expected behavior? Can anyone expand on this issue?
>
> -- elijah
>
> P.S. I am running 12.0(x)S on 7200 and 7500.



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