[arin-ppml] Number of routes, IPv6 vrs IPv4.

[William Herrin]

On Sun, May 31, 2009 at 12:11 PM, Leo Bicknell<bicknell at ufp.org> wrote:
> There as recently been a lot of press about the Cisco 6500 "Sup720-3B"
> platform.  This platform uses TCAM
> (http://en.wikipedia.org/wiki/Content-addressable_memory#Ternary_CAMs) to
> hold routing information so that switching decisions can be made
> at high speed.  This is fairly expensive memory.  The reason this
> made press is there is only enough TCAM to hold 256,000 IPv4 routes,
> and the IPv4 routing table is now up in the 290,000 range.  You can
> find lots of articles about how folks are choosing to throw away
> prefixes to fit in the TCAM limit.

Here's a great article for understanding exactly how TCAMs work. Once
you understand how they work, its fairly obvious why TCAMs are so
expensive compared to generic DRAM.

http://www.pagiamtzis.com/cam/camintro.html

Regards,
Bill Herrin



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