Hi,
I have one doubt about the following rfc3618
discription.
Suppose the router has three msdp peer: A, B, C.
A is RP(maching the first check
condition)
B is eBGP NEXT_HOP(maching the
second check condition)
C is iBGP advertiser(maching the third
check condition)
1. Which one is rpf peer? A, B, C, or all of
them.
Suppose all of them forward the same SA message,
does the router accept all of them or only one?
2. If above RPF Peer preference
is A>B>C, What can we do if a SA is received from lower preferred RPF Peer
first and SA would be never received from the highest preferred RPF Peer because
of the highest one’s SA advertising policy.
Thanks a lot.
10.1.3. Peer-RPF Forwarding
Rules
An SA message originated by R
and received by X from N is accepted if
N is the peer-RPF neighbor for
X, and is discarded otherwise.
MPP(R,N)
MP(N,X)
R
---------....-------> N ------------------> X
SA(S,G,R)
SA(S,G,R)
MP(N,X) is an MSDP
peering between N and X. MPP(R,N) is an MSDP
peering path (zero or more MSDP
peers) between R and N, e.g.,
MPP(R,N) = MP(R,
A) + MP(A, B) + MP(B, N). SA(S,G,R) is an SA
message for source S on group G
originated by an RP R.
The peer-RPF
neighbor N is chosen deterministically, using the first
of the
following rules that matches. In particular, N is the RPF
neighbor of X
with respect to R if
(i). N == R
(X has an MSDP peering with R).
(ii). N is the eBGP
NEXT_HOP of the Peer-RPF route for R.
(iii). The Peer-RPF route
for R is learned through a distance-vector
or path-vector routing protocol (e.g., BGP, RIP, DVMRP) and N
is the neighbor that advertised the Peer-RPF route for R
(e.g., N is the iBGP advertiser of the route for R), or N is
the IGP next hop for R if the route for R is learned via a
link-state protocol (e.g., OSPF [RFC2328] or IS-IS
[RFC1142]).
(iv). N resides in
the closest AS in the best path towards R. If
multiple MSDP peers reside in the closest AS, the peer with
the highest IP address is the rpf-peer.
(v). N is
configured as the static RPF-peer for R.
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