300-510 · Question #202
Which technique should be permitted on ASA Firewall to allow MSDP Peering?
The correct answer is B. TCP socket(s) carrying MSDP messages. MSDP (Multicast Source Discovery Protocol) is used to connect PIM-SM domains by allowing Rendezvous Points (RPs) in different domains to exchange information about active multicast sources. MSDP peers communicate over TCP using port 639. Because TCP provides reliable, connection-
Question
Which technique should be permitted on ASA Firewall to allow MSDP Peering?
Options
- APIMv2 messages carrying MSDP messages
- BTCP socket(s) carrying MSDP messages
- CMulticast BGP carrying MSDP messages
- DUDP socket(s) carrying MSDP messages
How the community answered
(38 responses)- A3% (1)
- B89% (34)
- C5% (2)
- D3% (1)
Explanation
MSDP (Multicast Source Discovery Protocol) is used to connect PIM-SM domains by allowing Rendezvous Points (RPs) in different domains to exchange information about active multicast sources. MSDP peers communicate over TCP using port 639. Because TCP provides reliable, connection-oriented transport, MSDP SA (Source Active) messages are delivered reliably between RPs. To allow MSDP peering through an ASA firewall, the administrator must create an access rule permitting TCP connections on port 639 between the peering RP addresses. MSDP does not use UDP (ruling out option D), does not ride inside PIMv2 messages (ruling out option A), and is not carried by Multicast BGP (ruling out option C) - though MBGP is often deployed alongside MSDP to carry multicast routing information.
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