[c-nsp] CEF CPUHOG on GSR 12.0(S)

[Tassos Chatzithomaoglou]

It could be this too:

CSCea12960
Externally found enhancement (Sev6) bug: Assigned (A)
Short mask prefixes cause CPUHOG in CEF LC IPC Background

In an network environment which has a default route (0.0.0.0/0) present, the
advertisement of a short mask prefix (x.x.x.x/1) will result in a CPUHOG
on Engine 4 or Engine4+ linecards each time the route is advertised or
withdrawn.

%SYS-3-CPUHOG: Task ran for 3660 msec (1/1), process = CEF LC IPC Background,
PC = 400DC1D0.

This behaviour is seen on IOS releases 12.0(21)S onwards.

Workaround: Prefix filters in BGP applied at the edge of the network can be used
to block short mask prefixes. This will not prevent the route being advertised
via an IGP.


--
Tassos


David Freedman wrote on 14/10/2007 3:34 μμ:
> Recently we've been seeing some messages in the log with regards to
> a CPUHOG event occuring on some engine 2 linecards we have running.
> 
> It didn't seem to be traffic affecting, and looked a little like this:
> 
> SLOT 6:Oct 12 03:17:41 DST: %SYS-3-CPUHOG: Task ran for 7312 msec (0/0),
> process = CEF LC IPC Background, PC = 400FC324.
> 
> Box is running 12.0(32)S5 and has not logged these messages before.
> 
> This slot faces an upstream provider.
> 
> Upon speaking with another provider, running 12.0(32)S6, they have
> been seeing the same messages on their kit but not at the same times, on
> E2 linecards facing an IXP, they are running S6.
> 
> We are both running IPv6 and I have all routing messages filtered on the
> upstream port (in case this was related to any RH0 nastyness)
> 
> #sh ipv6 access-list
> IPv6 access list bogons6
>     deny ipv6 any any routing sequence 10
> <snip>
> 
> One thing of note is that this could be related to bugid CSCsb12281 but
> this does not seem to effect S6, could any friendly cisco people on here
> expand a bit on this bug?
> 
> Many thanks,
> 
> Dave.
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