[c-nsp] IPv6 not Fast/CEF-switched on 3640 12.3T

[Oliver Boehmer (oboehmer)]

Daniel Roesen <> wrote on Monday, February 28, 2005 3:10 AM:

> Hi,
> 

> So basically all IPv6 traffic out of this interface is being
> process-switched. Why?
>
> The multicast traffic is received on GRE Tunnel102 and forwarded to
> the FastEthernet0/0. Traffic level is low though:
> 
> Tunnel102 is up, line protocol is up
>   Tunnel protocol/transport GRE/IP, key disabled, sequencing disabled
>   5 minute input rate 122000 bits/sec, 111 packets/sec
>   5 minute output rate 0 bits/sec, 0 packets/sec
> 
> Any unicast traffic transitting the box then has some 1.8-1.9 seconds
> RTT rise and ~25% packet loss.
> 
> In a different thread I think I've read that the 3640 maxes out at
> ~200pps process switching. This sounds reasonable when looking at the
> CPU load while switching the ~110pps multicast traffic.
> 
> But I wonder why all that is being switched process-level and not CEF?
> Is IPv6 multicast still non-CEF on 3640 with 12.3T? IPv6 unicast
> traffic received from the GRE tunnel is also sent to the FastE
> process-switched. 

I think IPv6 (unicast or multicast) over an IPv4 GRE tunnel is not yet
CEF-switched, "show cef not" should show increased counters in
"Unsupported" column.

> Sidenote: incoming IPv6 traffic isn't being counted in the switching
> stats properly, is that normal?

This is possibly related to the yet unsupported feature.

Can you use a different tunnel encaps? ipv6-over-ipv4 (tunnel mode
ipv6ip) should provide better results..

	oli