Subject: [magma] PIM-SM Neighborship

From: "Viswanathan, Magesh" <[email-masked]>
Date: Fri, 6 Jan 2006 23:22:05 +0530

Hi,
Have a question on draft for pim-sm v2(rev11).

1. Should PIM-SM depend on unicast routing protocol neighborship state-machine to build its own neighborship?
2. If No, then why?
3. Consider the following scenario which might happen if pim-sm is independantly building its neighborship.
    A and B are back-2-back connected and have pim enabled on their interface. Both send hellos to each other. Assume, due to some layer 2 issue A's hellos are not travelling up the stack in B. Hence, B could not participate in DR election on this interface. But B's hellos are received by A and according to DR election rules, A decides that B is the DR (since priority values are same, and B's IP addr is higher than that of A's). 

According to pim-sm v2 draft's (rev 11, section 4.3) recommendation this seems to be an issue when put in practice. 
1. Does anyone know a solution?
2. Why can't pim-sm have neighborship mechanism as followed by dmvrp where, each rtr adds his peer as neighbor only after 
seeing his own ip addr in the hellos recieved.

PS: 
1. In the above scenario, OSPF of A does not show B in 'FULL' state and so ospf neighborship is not up.
2. This is not a hypothetical question. I can simulate the issue in our implementation.

thanks,
magesh.

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