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

William Herrin bill at herrin.us
Mon Jun 1 00:48:07 EDT 2009

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.


Bill Herrin

William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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