We have a Catalyst 6513 with a Supervisor Engine 720 10GE (VS-S720-10G-3C), running IOS Version 12.2(33)SXI (s72033_rp-ADVENTERPRISEK9_WAN-M).

At friday morning we added our first 10G interface card: WS-X6708-10GE-3CXL

From this time, 'ipv6 dhcp relay destination' on our VLAN interfaces stopped working.

There were no special configuration changes made, just two trunk mode interfaces:

interface TenGigabitEthernet12/1
switchport
switchport trunk encapsulation dot1q
logging event link-status
logging event trunk-status
logging event spanning-tree status
udld port aggressive
end

I used a packet sniffer and found out that:

- On one VLAN, DHCPv6 solicit messages are relayed, an advertisement reaches the client, but all request messages do not arrive at the DHCP servers

- On another VLAN, even solicit messages are not relayed

A made a diff between the switches configuration from last week and now and I didn't find any differences - except the two interfaces Te12/1 and Te12/2.

I will try to reconnect both 10G trunks to the Sup again (like before) and pull the X6708 to see if DHCPv6 relay works again, but I'm pretty sure that this card started the trouble (we have short lease times and I can see that all DHCPv6 clients stopped working at the exact time of the card insertion).

Any clue what might cause this strange behaviour?

Thanks