CCNP CCNP Multicast and IPv6 2 — Questions and Answers
Question 1: What is the role of the Rendezvous Point (RP) in PIM Sparse Mode (PIM-SM)?
- Acts as the meeting point where sources register and receivers join to establish multicast distribution trees (Correct answer)
- Forwards all multicast traffic using dense-mode flooding
- Provides IGMP proxy services for downstream hosts
- Maintains the multicast routing table for the entire AS
Correct answer: Acts as the meeting point where sources register and receivers join to establish multicast distribution trees
The RP in PIM-SM is the central point where sources register their multicast streams and receivers send join messages to form the shared tree.
Question 2: Which protocol do hosts use to signal their membership in a multicast group to a local router?
- IGMP (Internet Group Management Protocol) (Correct answer)
- PIM (Protocol Independent Multicast)
- MOSPF (Multicast OSPF)
- DVMRP (Distance Vector Multicast Routing Protocol)
Correct answer: IGMP (Internet Group Management Protocol)
IGMP is used between hosts and their directly connected multicast routers to report group membership and receive multicast traffic.
Question 3: What is the multicast address range defined by IANA for general use?
- 224.0.0.0 to 239.255.255.255 (Correct answer)
- 224.0.0.0 to 224.0.0.255
- 230.0.0.0 to 239.255.255.255
- 225.0.0.0 to 232.255.255.255
Correct answer: 224.0.0.0 to 239.255.255.255
The full IPv4 multicast address range is 224.0.0.0 to 239.255.255.255 (Class D), though specific sub-ranges are reserved for link-local, global, and administratively scoped use.
Question 4: What is the purpose of the RPF (Reverse Path Forwarding) check in multicast routing?
- Ensures multicast packets arrive on the interface that the router would use to reach the source, preventing loops (Correct answer)
- Verifies that the RP is reachable before forwarding traffic
- Checks that the multicast group address is valid before accepting traffic
- Validates IGMP membership reports from downstream hosts
Correct answer: Ensures multicast packets arrive on the interface that the router would use to reach the source, preventing loops
RPF check prevents multicast routing loops by only accepting multicast packets that arrive on the correct upstream interface toward the source.
Question 5: What is Source-Specific Multicast (SSM)?
- A multicast model where receivers specify both the group address and the specific source they want to receive from (Correct answer)
- A method where the source registers with multiple RPs simultaneously
- A PIM mode that uses dense flooding before switching to sparse mode
- An IGMP extension that supports source filtering at the host level only
Correct answer: A multicast model where receivers specify both the group address and the specific source they want to receive from
SSM uses the 232.0.0.0/8 address range and allows receivers to specify the exact (S,G) source-group pair, eliminating the need for an RP.
Question 6: What is Auto-RP and what problem does it solve in PIM-SM networks?
- A Cisco-proprietary mechanism that dynamically announces and discovers RP information, eliminating static RP configuration (Correct answer)
- A feature that automatically tunes PIM hello intervals based on network topology
- A protocol that selects the RP based on the highest IP address among all routers
- An IETF standard for RP failover using redundant RP pairs
Correct answer: A Cisco-proprietary mechanism that dynamically announces and discovers RP information, eliminating static RP configuration
Auto-RP uses Candidate-RP announcements sent to 224.0.1.39 and RP-Discovery messages at 224.0.1.40 to dynamically distribute RP information across the network.
CCNP CCNP Multicast and IPv6 2
What is the role of the Rendezvous Point (RP) in PIM Sparse Mode (PIM-SM)?