Which of the following protocols is used for inter-domain multicast routing and natively supports
“source-specific multicast” (SSM)?

A.
BGMP

B.
DVMRP

C.
OSPF

D.
EIGRP

Explanation:

BGMP stands for border gateway multicast protocol. It is used for inter-domain multicast routing
and natively supports “source-specific multicast” (SSM). In order to support “any-source multicast”
(ASM), BGMP builds shared trees for active multicast groups. This allows domains to build
source-specific, inter-domain, distribution branches where needed. BGMP uses TCP as its
transport protocol, which helps in eliminating the need to implement message fragmentation,
retransmission, acknowledgement, and sequencing.
Answer option B is incorrect. The Distance Vector Multicast Routing Protocol (DVMRP) is used to
share information between routers to transport IP Multicast packets among networks. It uses a
reverse path-flooding technique and is used as the basis for the Internet’s multicast backbone
(MBONE). In particular, DVMRP is notorious for poor network scaling, resulting from reflooding,
particularly with versions that do not implement pruning. DVMRP’s flat unicast routing mechanism
also affects its capability to scale.
Answer option D is incorrect. EIGRP is a Cisco proprietary protocol. It is an enhanced version of
IGRP. It has faster convergence due to use of triggered update and saving neighbor’s routing
table locally. It supports VLSM and routing summarization. As EIGRP is a distance vector protocol,
it automatically summarizes routes across Class A, B, and C networks. It also supports multicast
and incremental updates and provides routing for three routed protocols, i.e., IP, IPX, and
AppleTalk.

Answer option C is incorrect. Open Shortest Path First (OSPF) is a routing protocol that is used in
large networks. Internet Engineering Task Force (IETF) designates OSPF as one of the Interior
Gateway Protocols. A host uses OSPF to obtain a change in the routing table and to immediately
multicast updated information to all the other hosts in the network.