American Fibertek SM8P-SFP User Manual

Page 29

Rev.A1

18-May-11

2-1-5. IP Address Assignment

For IP address configuration, there are three parameters needed to be filled

in. They are IP address, Subnet Mask, Default Gateway and DNS.

IP address:

The address of the network device in the network is used for internetworking

communication. Its address structure looks is shown in the Fig. 2-11. It is “classful”
because it is split into predefined address classes or categories.

Each class has its own network range between the network identifier and

host identifier in the 32 bits address. Each IP address comprises two parts: network
identifier (address) and host identifier (address). The former indicates the network
where the addressed host resides, and the latter indicates the individual host in the
network which the address of host refers to. And the host identifier must be unique
in the same LAN. Here the term of IP address we used is version 4, known as IPv4.

32 bits

Network identifier

Host identifier

Fig. 2-11 IP address structure

With the classful addressing, it divides IP address into three classes, class A,

class B and class C. The rest of IP addresses are for multicast and broadcast. The
bit length of the network prefix is the same as that of the subnet mask and is
denoted as IP address/X, for example, 192.168.1.0/24. Each class has its address
range described below.

Class A:

Address is less than 126.255.255.255. There are a total of 126 networks can

be defined because the address 0.0.0.0 is reserved for default route and
127.0.0.0/8 is reserved for loopback function.

Bit #

0 1

7 8

Network address

Host address

Class B:

IP address range between 128.0.0.0 and 191.255.255.255. Each class B

network has a 16-bit network prefix followed 16-bit host address. There are 16,384
(2^14)/16 networks able to be defined with a maximum of 65534 (2^16 –2) hosts
per network.