subnet prefix length > 64 breaks IPv6?

sthaug at sthaug at
Sat Jan 7 13:24:28 UTC 2012

>  "Note: An IPv4 route requires only one TCAM entry. Because of the
>     hardware compression scheme used for IPv6, an IPv6 route can take
>     more than one TCAM entry, reducing the number of entries forwarded
>     in hardware. For example, for IPv6 directly connected IP addresses,
>     the desktop template might allow less than two thousand entries."
> Translated: "The stated numbers for IPv6 routes are twice the real max.
> However, prefix compression may give better utilisation under certain
> conditions".

Thanks, that's the first *specific* information I've seen of equipment
that might have problems (reduced number of entries) with longer than
64 bit prefixes. Fortunately we're not using 3560/3750 for IPv6 routing
at the moment.

Any other takers?

Steinar Haug, Nethelp consulting, sthaug at

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