Multicast traffic not forwarded on Catalyst 6509E VSS Supervisor Engine 720 10GE.

Unanswered Question

Hi all.
I have two Catalyst 6509-E in VSS mode with VS-S720-10G-3C running 12.2(33)SXI3 ADV ENT SERVICES.
I'm using VRF-Lite also.
IP multicast routing and IGMP snooping are disabled.
Multicast source and client are on the same vlan, same switch and same linecard, so the IP-multicast traffic only needs to be Layer 2 switched.
May be I need to configure IGMP snooping querier on L3 interface.

interface Vlan11
ip vrf forwarding VRF-MC
ip address .....

Router1serv#show ip igmp vrf VRF-MC interface vlan 41
% Multicast not enabled for vrf VRF-MC

Does anybody could confirm that I'm affected by bug CSCtb58820?

Many thanks.

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Giuseppe Larosa Thu, 01/21/2010 - 13:18

Hello Andrea,

if IGMP snooping is disabled for the Vlan you don't need to configure an IGMP querier.

the bug says:

Multicast and unicast packets get dropped on Cisco WS-C6509-E with VS-S720-10G running s72033-adventerprisek9_wan-mz.122-33.SXI2a during steady state run (All learning and SPT built

is unicast traffic affected in your case or not?

if it is affected, your condition is likely similar to that described in the bug and you can try to apply the workaround described there

Hope to help


Giuseppe Larosa Fri, 01/22/2010 - 03:32

Hello Andrea,

source and client are in the same vlan, if source starts to transmit and you place a PC on another port in same vlan can you see the multicast stream?

You say that flooding  in the vlan is happening but client doesnt receive. This is strange.

Can you check the interface counters on the port to the client you should have separate multicast packets counters.

Also trying with another PC to see if there is any difference in comparison to uffiicial client.

or mirroring the port to the client with a SPAN session to see what is sent out the port.

I wonder if the port to the client may show output drops during flooding and client may be sensible to packet losses.

Hope to help


Sorry for my english!

Yes Giuseppe, server and client are in the same vlan but flooding is not happening (but should be!)

Show interface command shows me received multicast packets

show interface g1/0/29 (server)

     Received 7923244 broadcasts (7923244 multicasts)

show interface g1/0/30 (client)

     57490 packets output, 5385595 bytes, 0 underruns

without drop packet.



Giuseppe Larosa Fri, 01/22/2010 - 08:33

Hello Andrea,

clearly flooding is not taking place.

what happens if you enable ip multicast routing, ip multicast routing for the VRF, and IP IGMP on the vlan involved?

let's see if something changes

Hope to help


Giuseppe Larosa Wed, 02/03/2010 - 10:24

Hello Andrea,

you have been very kind to provide a feedback on this issue.

This case had an happy end and it is important to provide the solution it may help other people having the some trouble in the future

Best Regards



This Discussion