Managing HP Serviceguard for Linux, Tenth Edition, September 2012

Interface ID = Interface Identifier.
Link-Local Addresses
Link-local addresses have the following format:
Table 16
64 bits54 bits10 bits
interface ID01111111010
Link-local address are supposed to be used for addressing nodes on a single link. Packets
originating from or destined to a link-local address will not be forwarded by a router.
Site-Local Addresses
Site-local addresses have the following format:
Table 17
64 bits16 bits38 bits10 bits
interface IDsubnet ID01111111011
Link-local address are supposed to be used within a site. Routers will not forward any
packet with site-local source or destination address outside the site.
Multicast Addresses
A multicast address is an identifier for a group of nodes. Multicast addresses have the
following format:
Table 18
112 bits4 bits4 bits8 bits
group IDscopflags11111111
“FF” at the beginning of the address identifies the address as a multicast address.
The “flags” field is a set of 4 flags “000T”. The higher order 3 bits are reserved and
must be zero. The last bit ‘T’ indicates whether it is permanently assigned or not. A value
of zero indicates that it is permanently assigned otherwise it is a temporary assignment.
The “scop” field is a 4-bit field which is used to limit the scope of the multicast group.
For example, a value of ‘1’ indicates that it is a node-local multicast group. A value of
‘2’ indicates that the scope is link-local. A value of “5” indicates that the scope is site-local.
The “group ID” field identifies the multicast group. Some frequently used multicast groups
are the following:
All Node Addresses = FF02:0:0:0:0:0:0:1 (link-local)
All Router Addresses = FF02:0:0:0:0:0:0:2 (link-local)
All Router Addresses = FF05:0:0:0:0:0:0:2 (site-local)
IPv6 Address Types 331