Multicast Configuration on router

Unanswered Question
Oct 11th, 2008

1. I want to know when there is a multilink, do we need to configure the ip pim sparse-mode command on multilink also or just the 2 serial links?

2. Also, if there is a sub-interface s0.1 used for wan links, shall we configure the ip pim sparse-mode command there also, or not needed?


  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Giuseppe Larosa Sat, 10/11/2008 - 11:05

Hello Srinath,

1) on the multilink interface is needed is the only interface with a L3 config I don't think on member links is effective (they have "no ip address")

2) yes, again the subinterface has the L3 config and the physical interface shouldn't have ip address in most scenarios

Hope to help


durga_suji Sat, 10/11/2008 - 11:20

Hi Giuseppe,

thanks for the quick reply..

to be on the safer sife, is it okay to configure the ip pim sparse-mode on both physical interface and logical interface(multilink and sub-interface? or not needed?


Giuseppe Larosa Sat, 10/11/2008 - 12:44

Hello Srinath,

it is only needed on the subinterface and on the multilink because they are the only ones to understand what ipv4 multicast is and to handle IP packets.

I think that adding the command to the physical interface is really not needed.

You can add the command to the member links just to help read the configuration and as a safety measure for some cases where you need tochange the switching mode (if you need to disable CEF for troubleshooting)

Hope to help



This Discussion