Solved: Multicast igmp join group

cer43tcent · ‎05-08-2017

Hi All. I have a hub and spoke topology where there's a L3 switch with multiple L2 switches trunked to it. Also, there are several VLANs in use.

For the L3 switch I have

ip multicast-routing

ip pim rp-address 1.1.1.1

each vlan

ip pim sparse-dense-mode

Using different subnets for sender and receiver I can receive a multicast video stream given the above configuration without issue. Also, if I were to use the ip igmp join-group on each VLAN I still receive the stream no problem. My question is what does stating ip igmp join-group x.x.x.x under an interface do?

Reza Sharifi · ‎05-08-2017

Hi,

Have a look at the config guide for usage and explanation;

Use the ip igmp join-group command to configure an interface on the router to join the specified group or channel. With this method, the router accepts the multicast packets in addition to forwarding them. Accepting the multicast packets prevents the router from fast switching.

Link:

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti/command/imc-cr-book/imc_i1.html#wp2941931051

HTH

View solution in original post

Reza Sharifi · ‎05-08-2017

Hi,

Have a look at the config guide for usage and explanation;

Use the ip igmp join-group command to configure an interface on the router to join the specified group or channel. With this method, the router accepts the multicast packets in addition to forwarding them. Accepting the multicast packets prevents the router from fast switching.

Link:

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti/command/imc-cr-book/imc_i1.html#wp2941931051

HTH

cer43tcent · ‎05-08-2017

Thanks Reza. I had come across a recent post that also gave a good explanation.

https://supportforums.cisco.com/discussion/13236621/ip-igmp-static-group-and-igmp-join-group-configurations