[Xorp-hackers] RPF check in PIM-SM

[Chintan Shah]

Hello,

We are trying to implement a fast repair mechanism for PIM-SM  multicast
trees.
For that I need to know when is the RPF check performed on a received
packet. From whatever I could gather,
I understand that the kernel first tries to find a matching (S,G) entry in
the MFC table and if  it is  found then it
matches the incoming interface for the packet with the actual interface  on
which the packet was received and if both are  same then forwards the packet
to the outgoing interfaces from the outgoing interface list. My question is
whether this is the only RPF check that is performed on the packet or is
there any
other check involved like looking up the unicast table and then checking the
reverse path to the source
I am asking this question because the solution that we implemented is to
install the MFC entries
manually and there is  chance that the unicast table might be pointing to a
different interface than the MFC entry that we installed.
Could you please elaborate on how a multicast packet forwarded in the xorp
router.


Thanks a lot,
Chintan.
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