H3C Technologies H3C SecPath F1000-E - Manual (Page 66)

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Figure 3 Diagram for RPF check for SA messages
As illustrated in
Figure 3 , these MSDP peers dispose of SA messages according to the following RPF
check rules:
1. When RP 2 receives an SA message from RP 1
Because the source-side RP address carried in the SA message is the same as the MSDP peer address,
which means that the MSDP peer where the SA is from is the RP that has created the SA message, RP 2
accepts the SA message and forwards it to its other MSDP peer (RP 3).
2. When RP 3 receives the SA message from RP 2
Because the SA message is from an MSDP peer (RP 2) in the same AS, and the MSDP peer is the next
hop on the optimal path to the source-side RP, RP 3 accepts the message and forwards it to other peers
(RP 4 and RP 5).
3. When RP 4 and RP 5 receive the SA message from RP 3
Because the SA message is from an MSDP peer (RP 3) in the same mesh group, RP 4 and RP 5 both
accept the SA message, but they do not forward the message to other members in the mesh group;
instead, they forward it to other MSDP peers (RP 6 in this example) out of the mesh group.
4. When RP 6 receives the SA messages from RP 4 and RP 5 (suppose RP 5 has a higher IP address)
Although RP 4 and RP 5 are in the same AS (AS 3) and both are MSDP peers of RP 6, because RP 5 has
a higher IP address, RP 6 accepts only the SA message from RP 5.
5. When RP 7 receives the SA message from RP 6
Because the SA message is from a static RPF peer (RP 6), RP 7 accepts the SA message and forwards it
to other peer (RP 8).
6. When RP 8 receives the SA message from RP 7
A BGP or MBGP route exists between two MSDP peers in different ASs. Because the SA message is from
an MSDP peer (RP 7) in a different AS, and the MSDP peer is the next hop on the BGP or MBGP route
to the source-side RP, RP 8 accepts the message and forwards it to its other peer (RP 9).
7. When RP 9 receives the SA message from RP 8
Because RP 9 has only one MSDP peer, RP 9 accepts the SA message.