PIM Sparse Mode (PIM-SM) and PIM Source Specific Multicast (PIM-SSM) are supported without synchronizing PIM-SM or PIM-SSM states across the multichassis tunnel (MCT) cluster.
The PIM snooping mechanism snoops the Join and Prune messages that are exchanged in the MCT VLANs and learns the interested VLAN member interfaces. Optimal traffic forwarding is achieved with PIM snooping states synchronized between the MCT peers, using the BGP EVPN Join Sync method.
The Reverse Path Forwarding (RPF) check and L3 multicast route lookup are based on the unicast routing protocol running in the MCT cluster.
Note
The L3 PIM SM Multicast doesn't work for 232.0.0.1 - 232.255.255.255 after upgrade due to support of PIM-SSM.PIM-SM and PIM-SSM can be enabled on VLAN router interfaces that are extended over MCT. These VE interfaces act as normal PIM routers, and converge just like any PIM router in an L3 domain. PIM-enabled VE interfaces on these MCT VLANs see each other as peers. They can exchange Join and Prune messages natively to form the L3 multicast forwarding tree over the interchassis link (ICL).
PIM-SM and PIM-SSM control traffic travels over the ICL link of the cluster, encapsulated with the tunnel encapsulation method used by MCT. For example MPLS/VxLAN.
For PIM-SM, any MCT node can be the rendezvous point (RP) and root of the shared multicast tree. This RP can be a PIM router on a VE interface for any extended VLAN, or it can be any other PIM-enabled L3 interface on the MCT node. Generally a PIM-enabled loopback interface performs the RP functionalities. All other functions of PIM are supported natively, such as FHR source registration, LHR thresholding and SPT switch-over, BSR protocol, and Anycast RP functionality.
SSM reserved(default) range 232.0. 0.0 through 232.255. 255.255
Non-SSM(non-default range) range is 224.0.0.0 to 231.255.255.255 -233.0.0.0 -239.255.255.255.
Before 20.2.3g code, with 18r200bd code, SSM(Source-Specific Multicast) support was not there and both default(Reserved) SSM and Non-SSM default(non-reserved) groups where all groups come in one range from 224.0. 0.0 to 239.255. 255.255 that works with PIM sparse mode, which is programmed on the box appropriately.
The PIM Sparse mode configured with IGMP V2 or IGMP V3 are joined and processed with Tailend router LL-OC2-SLX2, and (*, G) is created. The PIM joins for the group are sent upstream
towards RP along the RPT=T. So PIM Sparse mode works for all SSM groups(232.1.4.1-250 to 232.1.0.1-250) and for other groups.
The new SSM features supported SSM (source-specific Multicast)
SSM default groups include 232.0.0.1-232.255.255.255, where the “ssm-enable” option is required for default-groups(reserved) groups to work.
The SSM is programmed with SSM reserved range by default. And If IGMP v3 joins from the non-default SSM groups on the Tailend router i.e., groups 224.0.0.0 to 231.255.255.255 and 233.0.0.0 -239.255.255.255(other than 232.0.0.1 to 232.255.255) then we need to use “ssm-enable range” option So SSM will work for non-default groups and default-groups.
Command usage:
“ssm-enable range <Prefix-list> “ or
“ssm-enable”
Since you have IGMP V3 reports and no IGMP v2 reports, it is better to configure
“range” for non-default(reserved) groups as below option1.
Therefore, the PIM SSM is configured and programmed for all the IGMP V3
receivers.
The PIM Hello packet over ICL is snooped for multicast router (mrouter) detection. With this information, traffic from a directly connected multicast source in the MCT VLAN, which has a non-designated router (DR) PIM router interface, can forward on the ICL port that was learned as mrouter. The PIM-DR on the other MCT node can see the source traffic and perform the FHR functionality, which registers the multicast source with the RP.