Multicast Flooding

Unanswered Question
Aug 26th, 2008
User Badges:

Hi I have 1x Catylist 3508G backbone swiitch and 11x 2950G when I set a powercast image running it floods the network how can I resolve this ?

All 2950G have IGMP snooping enabled


  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)

Do you have a RP set up as well? One of Cisco's documents on multicast states: "A router is still necessary with IGMP snooping to provide the IGMP querying."

I am guessing you just need to configure a router with 'ip multicast-routing' in config and 'ip pim dense-mode' on the locally facing interface.

andrew.butterworth Sun, 09/07/2008 - 03:00
User Badges:
  • Gold, 750 points or more

As Dan says you will need a Layer-3 device (per VLAN) that has IGMP enabled on it to act as the IGMP querier (and Multicast DR). Without this multicast will just flood. Also the 3508XL doesn't support IGMP snooping, only CGMP snooping so you would need to enable CGMP on the layer-3 device as well. The 3500XL series are EOL and you should really look at replacing this, maybe introduce a layer-3 core and solve the multicast issue as well?




This Discussion