[c-nsp] 6500 router hangs (IPV4 routing slows to a crawl) when IPV6 routing is enabled with VRFs.

[Nick Hilliard]

On 12/06/2012 15:21, Jim Trotz wrote:
> FIB TCAM maximum routes :   (BGP routes in table = 408K)
> =======================
> Current :-
> -------
> IPv4 + MPLS         - 512k (default)
> IPv6 + IP Multicast - 256k (default)

Jim,

when you enable ipv6 and when things slow down, can you post the output of
the following commands:

Router# show mls cef summary
Router# show platform hardware capacity forwarding

Also, as someone else pointed out, are you using ipv6 urpf?  This causes
all ipv6 packets on a PFC3 to be punted.  This is configured at the
interface using the command: "ipv6 verify unicast reverse-path".

Are you forwarding lots of ipv6 fragments?  These can also be
process-switched unless you use the "platform ipv6 acl fragment hardware
forward" command (don't enable this unless you understand the consequences
of it).

Finally, have you seen any sign of the following message in your logs:

%CFIB-7-CFIB_EXCEPTION: FIB TCAM exception, Some entries will be software
switched

This is the canonical message to say that you've bust your tcam limits and
basically everything on the box will be punted from there onwards.  The
only way to recover from this is to reload the router after configuring
your box not to bust its tcam limits.

Nick