Refer to the exhibit. Router R1 is configured to advertise outgoing SA messages to routers R2 and R3, but to receive incoming SA messages only from R2. Which additional configuration must an engineer

Question

Exhibit

Options

• AR1# ip msdp sa-filter in 192.168.3.1
• BR3# ip msdp sa-filter out 192.168.3.1
• CR3# ip msdp password peer 192.168.1.1
• DR1# ip msdp password peer 192.168.3.1

• A
  84% (42)
• B
  2% (1)
• C
  10% (5)
• D
  4% (2)

Explanation

MSDP (Multicast Source Discovery Protocol) uses SA (Source-Active) messages to share multicast source information between PIM-SM domains. The question states R1 already blocks incoming SA messages from R3 (the peer connected to Domain-C) - but the configuration to do so is missing. To filter all SA messages originating from Domain-C, the engineer must apply an inbound SA filter on R1 for the peer address 192.168.3.1 (R3's IP). The command 'ip msdp sa-filter in 192.168.3.1' on R1 instructs R1 to drop all incoming SA messages received from R3, effectively blocking Domain-C's multicast source advertisements. Option B is wrong because configuring a filter on R3 controls what R3 sends outbound, but the question asks for a configuration on R1 (and filtering at the source peer is less reliable than filtering at the receiving router). Options C and D reference MSDP peer passwords, which are for authentication, not filtering.

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