Novell LINUX ENTERPRISE SERVER 10 SP2 - INSTALLATION AND ADMINISTRATION Installation Manual page 575

Multicast
Addresses of this type relate to a group of network interfaces. Packets with such
an address are delivered to all destinations that belong to the group. Multicast ad-
dresses are mainly used by certain network services to communicate with certain
groups of hosts in a well-directed manner.
Anycast
Addresses of this type are related to a group of interfaces. Packets with such an
address are delivered to the member of the group that is closest to the sender, ac-
cording to the principles of the underlying routing protocol. Anycast addresses are
used to make it easier for hosts to find out about servers offering certain services
in the given network area. All servers of the same type have the same anycast ad-
dress. Whenever a host requests a service, it receives a reply from the server with
the closest location, as determined by the routing protocol. If this server should fail
for some reason, the protocol automatically selects the second closest server, then
the third one, and so forth.
An IPv6 address is made up of eight four-digit fields, each representing 16 bits, written
in hexadecimal notation. They are also separated by colons (:). Any leading zero bytes
within a given field may be dropped, but zeros within the field or at its end may not.
Another convention is that more than four consecutive zero bytes may be collapsed
into a double colon. However, only one such :: is allowed per address. This kind of
shorthand notation is shown in Example 30.3, "Sample IPv6 Address" (page 557), where
all three lines represent the same address.
Example 30.3 Sample IPv6 Address
fe80 : 0000 : 0000 : 0000 : 0000 : 10 : 1000 : 1a4
fe80 : 0 : 0 :
fe80 :
Each part of an IPv6 address has a defined function. The first bytes form the prefix and
specify the type of address. The center part is the network portion of the address, but
it may be unused. The end of the address forms the host part. With IPv6, the netmask
is defined by indicating the length of the prefix after a slash at the end of the address.
An address, as shown in Example 30.4, "IPv6 Address Specifying the Prefix Length"
(page 558), contains the information that the first 64 bits form the network part of the
address and the last 64 form its host part. In other words, the 64 means that the netmask
is filled with 64 1-bit values from the left. Just like with IPv4, the IP address is combined
with AND with the values from the netmask to determine whether the host is located
in the same subnetwork or in another one.
0 : 0 : 10 : 1000 : 1a4
: 10 : 1000 : 1a4
Basic Networking 557