Which two multicast address ranges are assigned as source-specific multicast destination
addresses and are reserved for use by source-specific applications and protocols? (Choose two.)
A.
232.0.0.0/8
B.
239.0.0.0/8
C.
232.0.0.0/4
D.
FF3x::/32
E.
FF2x::/32
F.
FF3x::/16
Explanation:
Source-specific multicast (SSM) is a method of delivering multicast packets in which the only
packets that are delivered to a receiver are those originating from a specific source address
requested by the receiver. By so limiting the source, SSM reduces demands on the network and
improves security.
SSM requires that the receiver specify the source address and explicitly excludes the use of the (*,
G) join for all multicast groups in RFC 3376, which is possible only in IPv4’s IGMPv3 and IPv6’s
MLDv2.
Source-specific multicast is best understood in contrast to any-source multicast (ASM). In the
ASM service model a receiver expresses interest in traffic to a multicast address. The multicast
network must
1. discover all multicast sources sending to that address, and
2. route data from all sources to all interested receivers.
This behavior is particularly well suited to groupware applications where
1. all participants in the group want to be aware of all other participants, and
2. the list of participants is not known in advance.
The source discovery burden on the network can become significant when the number of sources
is large.
In the SSM service model, in addition to the receiver expressing interest in traffic to a multicast
address, the receiver expresses interest in receiving traffic from only one specific source sendingto that multicast address.
This relieves the network of discovering many multicast sources and reduces the amount of
multicast routing information that the network must maintain.
SSM requires support in last-hop routers and in the receiver’s operating system. SSM support is
not required in other network components, including routers and even the sending host. Interest in
multicast traffic from a specific source is conveyed from hosts to routers using IGMPv3 as
specified in RFC 4607.
SSM destination addresses must be in the ranges 232.0.0.0/8 for IPv4 or FF3x::/96 for IPv6.http://en.wikipedia.org/wiki/Source-specific_multicast