V-251394

Discussion

When a new source starts transmitting in a PIM Sparse Mode network, the DR will encapsulate the multicast packets into register messages and forward them to the Rendezvous Point (RP) using unicast. This process can be taxing on the CPU for both the DR and the RP if the source is running at a high data rate and there are many new sources starting at the same time. This scenario can potentially occur immediately after a network failover. The rate limit for the number of register messages should be set to a relatively low value based on the known number of multicast sources within the multicast domain.

Check Content

Review the configuration of the DR to verify that it is rate limiting the number of multicast register messages.

If the DR is not limiting multicast register messages, this is a finding.

The following is a PIM sparse mode configuration example that limits the number of register messages for each (S, G) multicast entry to 10 per second.

ip multicast-routing
! 
interface FastEthernet 0/0 
description link to core
ip address 192.168.123.2 255.255.255.0
ip pim sparse-mode 
! 
interface FastEthernet 0/1
description User LAN
ip address 192.168.122.1 255.255.255.0
ip pim sparse-mode 
!
ip pim rp-address 1.1.1.1
ip pim register-rate 10