Your network contains a server that runs Windows Server 2008 R2. The server has the Streaming
Media Services role installed. The network is configured to use IPv6 only. You need to configure a
multicast stream. Which IPv6 prefix should you use?
A.
FD00::/8
B.
FE80::/10
C.
FEC0::/10
D.
FF00::/8
Explanation:
Multicast IPv6 addresses
A multicast address identifies multiple interfaces. With the appropriate multicast routing topology,
packets addressed to a multicast address are delivered to all interfaces that are identified by theaddress. IPv6 multicast addresses have the Format Prefix (FP) of 1111 1111. An IPv6 address is
simple to classify as multicast because it always begins with FF. Multicast addresses cannot be used
as source addresses. Beyond the FP, multicast addresses include additional structure to identify their
flags, scope, and multicast group, as shown in the following illustration.
The fields in the multicast address are as follows: Flags The Flags field indicates flags that are set on
the multicast address. The size of this field is 4 bits. As of RFC 2373, the only flag defined is the
Transient (T) flag. The T flag uses the low-order bit of the Flags field. When set to 0, the T flag
indicates that the multicast address is a permanently- assigned (well-known) multicast address
allocated by the Internet Assigned Numbers Authority (IANA). When set to 1, the T flag indicates that
the multicast address is a transient (not permanently assigned) multicast address.
Scope
The Scope field indicates the scope of the IPv6 internetwork for which the multicast traffic is
intended. The size of this field is 4 bits. In addition to information provided by multicast routing
protocols, routers use the multicast scope to determine whether multicast traffic can be forwarded.
The following scopes are defined in RFC 2373: Scope field value Scope
1 Node-local
2 Link-local
5 Site-local
8 Organization-local
E Global
For example, traffic with the multicast address of FF02::2 has a link-local scope. An IPv6 router never
forwards this traffic beyond the local link.
Group ID
The Group ID field identifies the multicast group and is unique within the scope. The size of this field
is 112 bits.
Permanently assigned group IDs are independent of the scope. Transient group IDs are only relevant
to a specific scope. Multicast addresses from FF01:: through FF0F:: are reserved, well-known
addresses.
To identify all nodes for the node-local and link-local scopes, the following multicast addresses are
defined:
FF01::1 (node-local scope all-nodes address) FF02::1 (link-local scope all-nodes address)
To identify all routers for the node-local, link-local, and site-local scopes, the following multicast
addresses are defined:
FF01::2 (node-local scope all-routers address) FF02::2 (link-local scope all-routers address) FF05::2
(site-local scope all-routers address)
With 112 bits in the Group ID, it is possible to have 2112 group IDs. However, because of the way in
which IPv6 multicast addresses are mapped to Ethernet multicast MAC addresses, RFC 2373
recommends assigning the Group ID from the low order 32 bits of the IPv6 multicast address and
setting the remaining original group ID bits to 0. By using only the low-order 32 bits in the group ID,
each group ID maps to a unique Ethernet multicast MAC address.
Source: http://technet.microsoft.com/en-us/library/cc781068.aspx
