Multicast RPF Question

Unanswered Question
Feb 29th, 2008

I am trying to set up multicasting using sparse-mode with Auto-RP. We basically have a 355012G or equivalent at each of our sites. Our WAN connection comes in on gi0/1 and then we use VLAN Interfaces to seperate subnets after that. I set up sparse-mode on both Gi0/1 and VLAN5 (the vlan interface I want to run multicast on). I set up a feed and am trying to ping that feed (after joining the group) and I can pink it fine using gi0/1 as a source, but not VLAN 5. It fails the RPF check. I have put a static mroute entry in "ip mroute [ip of VLAN 5 subnet] [ip of next hop interface i want to reach]. I am not sure of what to put for the "destination interface" of the ip mroute statement. We have a mesh through our cloud to all of our sites. Would I have to enter a ip mroute statement for all of the sites? Any help would be appreciated. I have attached some shows to show what is going on.



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Mohamed Sobair Fri, 02/29/2008 - 11:54

Hi,


The (IP mroute) command has different concept than a normal (IP route)command.


IP mroute, is used to reach a source rather than destination.


The RPF method indicate that if the incoming interface is not the outgoing interface for the multicast packet then the Multicast packet is dropped.


I can see that you need to influence the return multicast packet twoard the source through GigabitEthernet0/1.


Note: you will need to make sure of all RPF checks is not failed in all sites.


Ie:IP mroute (source of the group) G0/1



Hope it helps,

Mohamed

schadmin Fri, 02/29/2008 - 12:09

I tried using the "G0/1" on the mroute statemet before submitting this post but it said I couldn't do that...


Next hop IP address required for multi-access media.



Mohamed Sobair Fri, 02/29/2008 - 12:27

Hi,


There is two approach to influence a Multicast packet tward a source.


1- Creating end-to-end tunnel interface, and influencing a static route tward the RP which (is the source in this case).


2- you can modify the routing table desition locally, check if the RP prefix is could be influenced to be reachable via the same interface a multicast packet comes from. (This could be acheived by modifying normal routing path).


HTH

Mohamed

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