IPv6 Addressing

   


The current IP addressing structure, based on version 4 of the protocol, consists of a 32-bit address, made up of four groups of 8 bits. The address comprises a network address and a host address, depending on which class of network the address refers to. Figure 12.1 shows the current IP address structure:

Figure 12.1. The mapping of network and host addresses clearly shows the class structure in the 32-bit IPv4 protocol.

graphics\12fig01.gif

The current IP address is written as four decimal numbers separated by periods (.). An example of an IPv4 address is 210.127.36.133. This is a randomly chosen Class C address. The network number is 210.127.36, and the actual computer is host number 133 on that network; the network is subnetted on the expected boundary, which is ff:ff:ff:00.

IP addresses based on version 6 of the protocol consist of a 128-bit address made up of eight groups of 16 bits. As mentioned in the previous section, there are no classes, and the address is written as eight hexadecimal numbers separated by colons (:). The preferred format for writing IPv6 addresses is shown here: x:x:x:x:x:x:x:x.

Figure 12.2 shows the IPv6 address structure.

Figure 12.2. The 128 IPv6 address format shows that the entire structure is used to denote the address, without any network classes.

graphics\12fig02.gif

Because of the way in which some addresses are allocated, IPv6 addresses sometimes contain a number of empty (zero-filled) bits. The designers have taken this into account to make writing addresses easier by introducing a special syntax to denote "multiple groups of 16 bits filled with zeros." Thus, the following valid IPv6 addresses can be represented in two ways:

1040:FE3A:0:0:0:200:40C:8 OR 1040:FE3A::200:40C:8
0:0:0:0:0:0:0:A OR ::A
FF02:0:0:0:0:0:0:2 OR FF02::2

However, an IPv6 address could contain multiple blocks of 0, such as in 1080:0:0:0:4:0:0:2.

The use of the "::" to represent multiple groups of zeros can be used only once in an address, so the representation 1080::4::2 would be an invalid representation of the IPv6 address.

The IPv6 address structure also allows for a notation in which embedded IPv4 addresses can be written as part of a new IPv6 address. Consult the Appendix for more detailed information on the IPv6 address structure specification.


   
Top


Solaris System Management
Solaris System Management (New Riders Professional Library)
ISBN: 073571018X
EAN: 2147483647
Year: 2001
Pages: 101
Authors: John Philcox

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net