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Re: subnet prefix length > 64 breaks IPv6?
From: Glen Kent <glen.kent () gmail com>
Date: Wed, 28 Dec 2011 20:02:33 +0530

Most vendors have a TCAM that by default does IPv6 routing for netmasks <=64.

They have a separate TCAM (which is usually limited in size) that does
routing for masks >64 and <=128.

TCAMs are expensive and increase the BOM cost of routers. Storing
routes with masks > 64 takes up twice the number of TCAM entries as
the routes with masks <= 64. Since IPv6 is *supposed* to work with /64
masks, most vendors (usually the not-so-expensive-routers) provide a
smaller TCAM for > /64 masks.

Glen

On Wed, Dec 28, 2011 at 6:40 PM,  <sthaug () nethelp no> wrote:
On the other hand there's also the rule that IPv6 is classless and therefore routing on any prefix length must be 
supported, although for some implementations forwarding based on > /64 is somewhat less efficient.

Can you please name names for the "somewhat less efficient" part? I've
seen this and similar claims several times, but the lack of specific
information is rather astounding.

Steinar Haug, Nethelp consulting, sthaug () nethelp no



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