[c-nsp] Sup32 TCAM limit

[Peter Rathlev]

On Thu, 2008-06-26 at 09:48 +0200, Gregoire Huet wrote:
> Reading the previous threads on this topic, I have understood that the TCAM
> size would limit the number of routes on the Sup32 supervisor blade to 249k.
> 
> What I do not understand is what would happen to the routes being inserted
> above this limit. Would such routes be 'soft' routed ? Is there also a 
> treshold for

Prefixes that cannot fit in the TCAM are punted to the MSFC, and thus
software switched, probably in an interrupt based CEF path. Less
specific prefixes are punted before more specific. The Sup32 software
forwarding is very limited performance wise.

> I would appreciate to know your experience with this blade and the 
> increasing
> number of public IPv4 routes.

The Sup32 is really not useful as an Internet router anymore. For a
PFC-based system you need an XL-version, like the Sup720-3BXL, which can
hold 1 million routes. Otherwise you need a real software based router,
like the 7200, to do the job. This platform cannot give you the Sup32
performance though.

Regards,
Peter