Operating notes

Eliminating redundancy in support for a multicast group

Configuring only one router in a domain as an RP for supporting traffic for a specific multicast group eliminates support redundancy for that group. In this case, if that router becomes unavailable, the group will be excluded from the domain.

Excluding multicast groups

If all of the C-RPs and static RPs (if any) in a domain are configured to exclude some multicast groups or ranges of groups, multicast traffic for such groups will be dropped when received by a DR, and will not be forwarded to any RP. (Such groups will still be switched locally if IGMP is enabled on the VLAN where the excluded group traffic is received from a multicast traffic source.)

Routing table entries

For multicast traffic from a source to the edge router supporting a multicast receiver requesting the traffic, when an SPT forms, the routing table (on the edge router) will contain both of the following for the supported group:

  • (S,G) entry for the source IP address and IP multicast group address supported by the SPT.

  • (*,G) entry for the "any" (wildcard) source and (same) multicast group supported by the RP tree.

Flow capacity

The router supports up to 2046 flows. A router acting as a DR or RP has a significantly higher CPU load than other routers in a PIM-SM domain.

IP addresses acquired through DHCP

PIM-SM operation requires statically configured IP addresses and does not operate with IP addresses acquired from a DHCP server.