[c-nsp] igmp helper-address

[R S]

Hi

I’ve three routers in a broadcast
domain: A, B and C.

 

source ---- WAN ---- A ----- lan
----- C ---- receiver

                                                |

                                                B

 

A is the one where multicast traffic
arrives from WAN (and also RP in my lab), B is the PIM DR of the lan and C is
where igmp helper-address is configured (pim passive on the lan) pointing to A.


 

The only way to make the stub igmp
helper-address configuration on router C is to make A as PIM DR.

I’m wondering to understand the
reason ? 

 

Tks