[c-nsp] Cat 6500 - uRPF - FIB TCAM

Brandon Applegate brandon at burn.net
Tue Aug 14 19:50:08 EDT 2012


I know this has been mentioned over the years here and there, but I don't 
know that I fully understand the exact behavior.  I've always read 'urpf 
halves your tcam...'.  So this only applies to the interface on which it's 
configured, correct ?  So for example, in a single switch with the full 
routing table (using ipv4 for examples, and using simple even numbers 
not counting any built-in entries):

uplink 1 - 400k routes
uplink 2 - 400k routes

customer interface 1 - 2 routes
customer interface 2 - 2 routes

So this is 400,004 entries.  Adding (strict) urpf to the customer 
interfaces (not the uplinks) would make this 400,008 ?

I guess I'm just unsure of if urpf is added to a single interface (even a 
customer interface with 1 or 2 prefixes) - does this have some 'global' 
effect ?

Thanks in advance.

Brandon Applegate - CCIE 10273
PGP Key fingerprint:
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