Layer 3 IP Multicast using PIM-SM

Consider the following sample topology for MLAG (Multi-switch Link Aggregation Group):

DUT-1(core lic)======ISC vlan========DUT-2(core lic)

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+----------------DUT-3(edge lic)---------------+

DUT-1 and DUT-2 are MLAG peers, DUT-3 is a L2 switch whose uplink is a LAG (Link Aggregation Group) up to the pair of MLAG switches.

RP and BSR can be configured on same device along with the MLAG configuration, but we recommend to keep RP node away from MLAG peers. One MLAG peer will be Designated Router (DR) and another one will be elected as NON-DR for MLAG VLAN. DR node will send *,G and try to pull the traffic from RP, and Non-DR will not pull the traffic until DR is alive. If you config RP on Non-DR node then both MLAG peers will pull the traffic which triggesr the assert to avoid the traffic duplication. It is not recommended to setup RP on any VLAN on MLAG peers.
It is recommended to avoid the assert operation since a small amount of traffic duplication happens during the assert operation. We can avoid assert in some scenario but not all the scenarios.
DR priority configuration will help to make RP node as DR. The DR priority feature is available from 15.3.2 release onwards.
It is recommended that for PIM-SM deployments, the RP is configured on loopback VLANs instead of regular VLANs. This ensures continuous connectivity to the RP without needing active ports present in that respective VLAN.
It is recommended that for PIM-SM deployments, route-to-source must exist and receivers should get the traffic from the SPT tree in the MLAG configurations. *,G forwarding in MLAG is not a recommended configuration.

Published March 2020prev | next