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Question about RPF election

gongya001
Level 1
Level 1

I am labbing Multicast Assertion mechanism.

From https://www.cisco.com/c/en/us/support/docs/ip/ip-multicast/212595-how-well-do-you-know-pim-assert-mechanis.html 

McastAssert.JPG

Based on

the highest PIM neighbor behavior

R2 should be elected for  (*,G) , right ?

 

Why does the doc say "In the topology, R1 is the RPF neighbour towards the RP, hence R3 sends a (*,G) join towards R1." ?

 

R3#show ip mroute
IP Multicast Routing Table
Outgoing interface flags: H - Hardware switched, A - Assert winner, p - PIM Join
 Timers: Uptime/Expires
 Interface state: Interface, Next-Hop or VCD, State/Mode
(*, 239.1.1.1), 00:00:55/stopped, RP 192.168.0.100, flags: SJC
  Incoming interface: GigabitEthernet1, RPF nbr 192.168.3.1
  Outgoing interface list:
    GigabitEthernet4, Forward/Sparse, 00:00:55/00:02:04

(10.0.0.2, 239.1.1.1), 00:00:52/00:02:07, flags: JT
  Incoming interface: GigabitEthernet1, RPF nbr 192.168.3.2, Mroute
  Outgoing interface list:
    GigabitEthernet4, Forward/Sparse, 00:00:52/00:02:07
I can't duplicate two different RPF neighbors unless I customize the different routes for source.

 

thanks !!

1 Accepted Solution

Accepted Solutions

Hello

apologies typo - R2 Gi2

 


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

View solution in original post

4 Replies 4

Hello

On r3 Gi2 enabled to receive multicast? If it isnt then that's why R1 GI2 is at present the rpf for the RP


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

From that doc, it does not say which interfaces are enabled for multicast, I assume that all of them are enabled pim sparse mode.

Also R3 does not have Gi2, I do not know which interface you mean.

 

thanks for taking a look at it. !!

Hello

apologies typo - R2 Gi2

 


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

thanks !!

 

seems easy to understand assert for dense mode, but not for Sparse and SSM.

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