At 09:58 PM 5/20/2002 +0200, sthaug@nethelp.no wrote:
> > The TCAM that holds the FIB table is capable of holding 256,000 entries.
> > Without unicast RPF checking turned on the maximum number of unicast
> > entries that can be held in the hardware FIB table is 244,000. The
> > remaining 12,000 entries are reserved for multicast routes. If unicast RPF
> > checking is enabled then the number of routes that are held in the TCAM is
> > halved.
>
>Just so I am absolutely certain what happens here: Is the number of routes
>that are held in the TCAM simply halved *as soon as unicast RPF checking
>is turned on* (even for a single interface) - or are there other config
>parameters that are also relevant?
If you enable unicast RPF checking on a single interface it cuts the
routing table size in half. To perform unicast rpf checking optimally we
program the FIB table into the TCAM twice and this allows us to do the
unicast RPF check in parallel with the forwarding lookup.
Unicast RPF checking documentation for Sup2
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/12_1e/swconfig/secure.htm#xtocid26
Ian
>(If it only takes a single "ip verify unicast reverse-path", I guess I'll
>be converting our 6500s to use input ACLs instead.)
>
>Steinar Haug, Nethelp consulting, sthaug@nethelp.no
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