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New Member

Multicast Not Working with Tomcat Cluster

Hi everyone,

Has anyone experienced issues regarding multicast traffic for a Tomcat cluster not being seen as a source?

Currently have an any source multicast (ASM) design with hosts running IGMPv2, using PIM-SM with an RP configured. The servers in the tomcat cluster are virtualised and have both registered as listeners to the multicast group (, in a packet capture we can see the server sending out UDP traffic to but on the switch it does not get listed as a source. However, when I use a multicast testing tool to send out multicast traffic from the same server to it will then be seen as a source. Once I stop this tool however, it will cease to be a source.

In a packet capture I can't see anything different between what is being streamed by tomcat or the tool. I've tried disabling igmp snooping to see if that makes a difference, I've tried static multicast routes, I don't see anything alarming when I debug ip igmp and I have also tried a source specific multicast design using PIM-SSM with source address mapping and experience the same behaviour.

Does anyone have any suggestions or ideas? I can only think of opening a TAC case and try and get some assistance from them.




Hi Mark,

Hi Mark,

      If both of your cluster machines are in same VLAN/network , IGMP Querier feature should do for your requirement . 


Solution 2: Enable IGMP Querier Feature on a Layer 2 Catalyst Switch

The IGMP querier is a relatively new feature on Layer 2 switches. When a network/VLAN does not have a router that can take on the multicast router role and provide the mrouter discovery on the switches, you can turn on the IGMP querier feature. The feature allows the Layer 2 switch to proxy for a multicast router and send out periodic IGMP queries in that network. This action causes the switch to consider itself an mrouter port. The remaining switches in the network simply define their respective mrouter ports as the interface on which they received this IGMP query.

Switch2(config)#ip igmp snooping querier

Switch2#show ip igmp snooping querier 
Vlan      IP Address     IGMP Version   Port               
1        v2             Switch

Switch 1 now sees port Gig 2/46 linking to Switch 2 as an mrouter port.

Switch1#show ip igmp snooping mrouter 
vlan            ports
   1  Gi2/46

When the source on Switch 1 starts to stream multicast traffic, Switch 1 forwards the multicast traffic to the Receiver 1 found via IGMP snooping (i.e., out port Gig 2/48) and to the mrouter port (i.e., out port Gig 2/46).




New Member

Hi Sandy,Thanks for the

Hi Sandy,

Thanks for the response. The guests aren't on the same subnet/vlan/network, however the clustering does work when they are so we're confident we don't have an issue with the application. Attached is a diagram of the network that I have the multicast routing configured over.

Any further suggestions?

Kind regards,


New Member

The application was using a

The application was using a TTL value of "1" in it's packets, once this was increased to an appropriate number the original multicast configuration I had works.

Great .. Thanks your finding

Great .. Thanks your finding ..