Limiting the Group Ranges an RP Services

Problem

When configuring the RPs for a PIM-SM domain, you want to limit the address range so the router acting as the RP does not need to handle traffic for so many multicast groups.

Solution

Specify the group address range when you configure the RP:

	[edit protocols pim]
	aviva@RouterA# set rp local address 192.168.13.1 group-ranges 224.0.0.0/8

Discussion

When you configure a PIM router to be an RP, by default it is eligible to be the RP for all groups. For IPv4 the default group range is 224.0.0.0/4, and for IPv6 it is FF70::/12 to FFF0::/12. If some multicast groups are sending a lot of traffic, a single RP might become overwhelmed with handling it all. To minimize router overload and congestion, configure several RPs and have each one of them act as RP only for a limited range of group addresses.

This recipe shows how to limit an RP to handle only groups in the 224.0.0.0/8 range. To verify that the configuration has taken effect, look at the RP routers:

	aviva@RouterA>  
show pim rps
	Instance: PIM.master
	Address family INET
	RP address Type Holdtime Timeout Active groups Group prefixes
	192.168.13.1 bootstrap 150 None 4 224.0.0.0/8
	192.168.13.1 static 0 None 4 224.0.0.0/8
	Address family INET6

The Group prefixes column shows that this router is now RP only for the range 224.0.0.0/8. It is no longer RP for the default range of 224.0.0.0/4.

You can limit the group address range serviced by the RP regardless of the method you choose to establish the RP routers in your PIM-SM domain. The show pim rps output above tells you that the RP router was configured using a bootstrap router. You can also use the set rp local address group-ranges command if you configure the RP manually, with auto-RP, or with anycast.