subnet prefix length > 64 breaks IPv6?

sthaug at sthaug at
Wed Dec 28 19:46:48 UTC 2011

> IPv6 CEF appears to be functioning normally for prefixes longer than
> 64-bit on my 720(s).
> I'm not seeing evidence of unexpected punting.
> The CPU utilization of the software process that would handle IPv6
> being punted to software, "IPv6 Input", is at a steady %0.00 average
> (with spikes up to 0.02%).
> So there would seem to be at least one major platform that is OK.

And there are other platforms, e.g. Juniper M/MX/T, where there is no
concept of "punt a packet to software to perform a forwarding decision".
The packet is either forwarded in hardware, or dropped. IPv6 prefixes >
64 bit are handled like any other IPv6 prefixes, i.e. they are forwarded
in hardware.

Steinar Haug, Nethelp consulting, sthaug at

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