3Com Switch 8800 Configuration Guide Chapter 30 MSDP Configuration
30-3
this case, the last hop router connected with the group member in domain 3 can
choose whether to switch to SPT.
II. Message forwarding and RPF check between MSDP peers As shown in Figure 30-2 MSDP working principles (II), Switch A, Switch B, Switch C,
Switch D, Switch E and Switch F belong to domain 1, domain 2 and domain 3
respectively. MSDP peer relationship is established between them, indicated with
bi-directional arrows in the figure. Among them, Mesh Group is created among Switch
B, Switch C and Switch D.
AS 1
AS 2
AS 3
SwitchD
SwitchF
SwitchE
SwitchC
SwitchB
SwitchA
Source
mesh group
Static peer
Figure 30-2 MSDP working principles (II)
The SA message forwarding and RPF check among these MSDP peers are illustrated
as follows:
1) If the SA message is from a MSDP peer that is the RP of the multicast source as
from Switch A to Switch B, it is received and forwarded to other peers.
2) If the SA message is from a MSDP peer that has only one peer as from Switch B to
Switch A, it is received.
3) If the SA message is from a static RPF peer as from Switch D to Switch E, it is
received and forwarded to other peers.
4) If the SA message is from a MSDP peer in Mesh Group as from Switch B to Switch
D, it is received and forwarded to the peers outside the Mesh Group.
5) If the SA message is sent from a MSDP peer in a same domain, and the peer is
the next hop along the optimal path to the RP in the domain of source, as in the