Information Technology Reference
In-Depth Information
If the path is found, the IP address of the BGP peer that sent the best path is compared to
the MSDP peer address that sent the MSDP SA to the router that is performing the RPF
check. If the peer addresses are the same, the RPF check succeeds. If they are different, the
check fails.
Figure 11-19 shows an RPF check that succeeds.
Figure 11-19
Successful iBGP-Based MSDP SA RPF
Source
G: 224.1.1.1
ISP 3
ISP 2
R1
R2
BGP Peer
MSDP Peer
SA Message
R3
R4
ISP 1
R5
The MSDP SA shown in Figure 11-19, for the group 224.1.1.1, is received by R5 from R4,
which are iBGP peers, using the loopback0 interface for both the iBGP and MSDP peering.
The debug for the received MSDP SA is shown in Example 11-9. Using an i(m)BGP
neighbor for the RPF, the RPF check passes for the SA received from R4.
Example 11-9
MSDP Debugs Show That SA RPF Succeeds
*Mar 3 09:21:19.691: MSDP(0): 10.1.0.4: Received 20-byte msg 31 from peer
*Mar 3 09:21:19.691: MSDP(0): 10.1.0.4: SA TLV, len: 20, ec: 1, RP: 10.1.0.1
*Mar 3 09:21:19.691: MSDP(0): 10.1.0.4: Peer RPF check passed for 10.1.0.1,
used IMBGP peer
