multicast and IGMP

[kjbarrass]

Hi

I have posted a similar question below but this is a more simplified scenario.

If you have switched network with all ports on say vlan 10.

On this switched network are 2 pim-SM enabled routers and other devices.

If there are no multicast sources or multicast receivers such as PCs on this switched network and igmp snooping is enabled for vlan 10.

The 2 routers are in the same pim domain on of the two been the RP and a DR for vlan 10.

How will the switched network handle multicast traffic from one pim-sm router to another pim-sm if the sources and receivers are hanging off these routers and not on the switched network?

My concern is will the switches block multicast on vlan 10 between the routers vus breaking multicast between the two routers. My reasoning for this is will igmp snooping block forwarding the multicast due to there been no igmp joins/reports from interested devices or will the switches forward the traffic to the mrouter port.

Cheers, Kev

[hardiklodhia · Accepted solution]

Hi,

If a multicast group has only sources and no receivers in a VLAN, IGMP snooping constrains the multicast traffic to only the multicast router ports.

rgrds,

[kjbarrass]

thanks for that, this has been bugging me for a while. iam trying to figure out how multicast is treated by intermediate switches between us and another PIM-SM domain. If this is the case it is good meaning multicast is not getting flooded across our switches.

Regards

Kev