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Auto-RP is used in Protocol Independent Multicast sparse-mode environments to distribute rendezvous point information automatically. In PIM sparse mode, multicast routers must know which RP is responsible for specific multicast group ranges. Without a dynamic RP-discovery mechanism, administrators would have to configure RP information manually across routers. Auto-RP solves that by allowing candidate RPs to announce themselves and mapping agents to advertise group-to-RP mappings throughout the multicast domain. Therefore, option B is correct. Option A is incorrect because Auto-RP does not distribute IGMP traffic; IGMP operates between hosts and local multicast routers to manage group membership. Option C is wrong because Auto-RP does not automate leaf-router configuration generally; it specifically distributes RP mapping information. Option D is also inaccurate because Auto-RP does not perform an election in the same way as BSR. It advertises candidate RP and mapping-agent information so routers can learn RP mappings. The key ENCOR concept is multicast control-plane discovery for PIM sparse-mode RP selection. References/topics: ENCOR multicast, PIM sparse mode, Auto-RP, rendezvous point discovery, multicast group-to-RP mapping.

The correct answer is D.

OSPF and EIGRP use different multicast addresses for exchanging routing information:

OSPF uses:

224.0.0.5 → AllSPFRouters

224.0.0.6 → AllDRouters

EIGRP uses:

224.0.0.10

This is a well-known operational difference between the two protocols and is commonly tested in Cisco ENCOR.

A. OSPF uses IP protocol number 88. EIGRP uses IP protocol number 89. This is reversed.

EIGRP = IP protocol 88

OSPF = IP protocol 89

B. OSPF uses a default hello timer of 5 seconds. EIGRP uses a default hello timer of 10 seconds. This is incorrect.

On most broadcast and point-to-point networks, OSPF default hello = 10 seconds

EIGRP default hello = 5 seconds on high-speed links

C. OSPF uses an administrative distance of 115. EIGRP uses an administrative distance of 160. This is also incorrect.

OSPF AD = 110

EIGRP internal AD = 90

EIGRP external AD = 170

Memorize these protocol identifiers:

OSPF

Protocol number: 89

Multicast: 224.0.0.5 / 224.0.0.6

EIGRP

Protocol number: 88

Multicast: 224.0.0.10