Pruning FIB entries, on the other hand, can be done quite safely as long as you're willing to accept the conversion of "null route" to "don't care." Some experiments were done on this in the IETF a couple years back. Draft-zhang-fibaggregation maybe? Savings of 30% in typical backbone nodes looked possible. That's 30% of your TCAM reclaimable.
Hence the “when programming the TCAM” part of my original statement :)
For the moment it seems to be cheaper to just build bigger TCAMs. Cheaper for the router vendors anyway.
I think of it more like “why spend development dollars on a feature that will cause my customers to keep their existing hardware longer and delay upgrades?” Yes, vendors do think like that. -C
Regards, Bill Herrin
-- William Herrin ................ herrin@dirtside.com bill@herrin.us Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/> Can I solve your unusual networking challenges?