I'm currently studying multicast and I'm having a hard time thinking on how it would work on a HSRP environment.
Let's say for example I have 2 VLANs, VLANs 10 and 20. VLAN 10 uses 192.168.10.0/24 and VLAN 20 uses 192.168.20.0/24. The active HSRP MSFC always uses .2 and the standby uses .3. If for example the multicast source is in VLAN 10. Source in VLAN 10 will use a destination MAC that corresponds to the multicast IP it is using so both HSRP MSFCs (I'm assuming both) will receive the traffic. If for example there are no multicast clients in VLAN 20, the MSFC will know this thru IGMP right? If there are no clients that wants to join the group, the MSFC will not forward the traffic in VLAN 20. The IGMP querier will be the active MSFC since it is using a lower IP address which is 192.168.20.2. But for example, 1 host in VLAN 20 wants to join the group, it will send an IGMP membership report to 188.8.131.52 then MSFCs will start forwarding the multicast traffic, but this time, the standby MSFC will forward the traffic since it is the designated forwarder on the LAN because it has a higher IP address which is 192.168.20.3. I don't know if I got this correctly but please correct me if I'm wrong.
My another inquiry is, since the destination MAC address of the multicast source is a multicast MAC, both MSFCs will receive the traffic. Base from the previous scenario, the standby MSFC is the designated forwarder. Will the active router still process the received packets from the source? From what I'm thinking, it is still receiving the traffic in VLAN 10 but it doesn't forward the packets in VLAN 20 because of the Assert message processed in VLAN 20 and they both agree that standby MSFC will be the forwarder.
Please help me. Really having a hard time studying multicast. :-(
Thanks in advance.