[f-nsp] cam strangeness

Kristian Larsson kristian at juniks.net
Sun Mar 5 10:22:02 EST 2006

On Sun, Mar 05, 2006 at 11:23:04AM +0000, Stephen J. Wilcox wrote:
> Hi,
>  anyone know what this messages means:
> Warning: Shadow CAM data Entry (0x00001365: 0c90e7ff 00000000 (tag 9)) is found 
> at index 0x00003ff2!
no clue, although I've gotten them too.
> when displaying a cam entry (sh cam ip ....)
> there is also a valid cache entry found, the router is running b2r7.8.01a on a 
> BI4000 and has 'ip supernet agg' enabled

I thought I'd tell you about a small problems of
ours. We're using three BI4k in an ISP
environment, ie full bgp table and quite a lot of
traffic to different destinations.

What happens is that when the TCAM gets full
(which it does rather quickly despite aggregation)
the router stops forwarding traffic to certain
prefixes since it has no path to them.

When the TCAM is full the CPU is supposed to
remove an old entry and put in a new one, although
this will lead to cam trashing, ie the cpu will do
nothing but remove and fill the cam with new
routes it will at least work. Our foundry doesn't
insert a new route it merely sits there not
fowarding traffic to the given destination.
The problem has arisen quite recently, and it
occurs about ten to twenty times a day. Solution
is to insert a static route for the prefix that
does not work and then remove it again, this will
force an update of the CAM.

We've switched mgmt card, tried different
firmwares but to no avail.

Just though I'd let you know. We are moving to


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