subnet prefix length > 64 breaks IPv6?

sthaug at sthaug at
Wed Dec 28 14:41:14 UTC 2011

> 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.

Please provide references. I haven't seen any documentation of such an
architecture myself.

> 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.

Ah, but do the "not-so-expensive-routers" use TCAM at all?

Steinar Haug, Nethelp consulting, sthaug at

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