How to manage convergence - HSRP with Multicast

Say I am running Multicast in parallel to HSRP or VRRP. My HSRP Primary device is also PIM DR (Higher Pri). When PRI path goes down, the traffic falls back to backup path with HSRP, But PIM take times to converge. Later when Primary Link comes up, PIM again takes lot of time to converge considering it would wait for 105 secs (PIM HOLDDOWN).

Now part of solution could be using HSRP aware PIM but my client per say is running old IOS.


I am unable to find " ip pim hello-interval" in given IOS too though I found this command only in Nexus Multicast command ref but not IOS command ref.


How would you fix it ?


  • If the IOS code does not support HSRP aware PIM, i guess it does not support MoFRR either. If you can't change PIM timers, it also means that multicast subsecond convergence features are also not supported. To change the PIM hello interval use the interface-level command "ip pim query-interval", sub-second values could be supported based on the code; technically you should match the PIM timers with HSRP timers; also you need to make sure that routing converges first, before PIM, to ensure PIM trees are correctly rebuild. Of course you should also reconfigure IGMP timers on the hosts, as after PIM DR is re-elected, on the shared tree, the DR needs to see the IGMP message in order to trigger building the new shared tree for the group.

Sign In or Register to comment.