[c-nsp] VSS 1440 issues

[C and C Dominte]

Hi,

 

I recently clustered 2 Catalysts 6509's into a VSS 1440
Virtual switch.

 

Details about the cluster:

 

- Software version: 
s72033_rp Software (s72033_rp-IPSERVICESK9_WAN-M), Version 12.2(33)SXI1,
RELEASE SOFTWARE (fc3)

 

- Supervisor: 
VS-S720-10G  with one 10G port
used as VSL link

- Linecards Active chassis: 

                1 x
WS-X6708-10GE with one 10G used for the VSL link for redundancy

                4 x
WS-X6748-GE-TX 

 

- Linecards Standby chassis

                1 x
WS-X6708-10GE with one 10G used for the VSL link for redundancy

                2 x
WS-X6748-GE-TX 

                

The 6748 line cards are used and
configured for MEC Etherchannels. 

 

At the other end of the MEC
channels there are non-Cisco edge switches. The multi chassis Ether Channels
are configured as 2 x 1G links, and single switchport trunks are configured as
1 x 1G links. All vlans are allowed on the single switchport trunks and port
channels from VSS Cluster to the edge switches.

 

The issue is that unicast
traffic is flooded by the VSS Cluster across all trunks. The flooded traffic
generated by the VSS cluster is between 600mbps and 1gbps, and almost all of
the flooded traffic is unicast and has the source MAC address of the VSS
Cluster. However, if the trunk is a MEC, the unicast traffic is flooded only on
one switchport. All of the flooded ports in MECs are on switch 2 in the VSS
cluster. The only ports flooded in switch 1 are the ones that have a single
trunk instead of MEC.

 

We tried to investigate this on
a low importance link. The VSS cluster learned only 10 MAC addresses on one
edge trunk configured as 1 x 1G link. This edge trunk received the flood of
unicast traffic from the VSS cluster as well. During testing, this trunk was
modified manually on the VSS Cluster, to allow only 4 VLANS instead of all.
Allowing only 4 vlans on this trunk stopped the flood on the edge trunk and
stopped the flood on all other trunks as well.

 

Does anyone have any idea about
what can cause this?

 

Thanks

 

Catalin