3com 8807 User Guide
Configuring IP Address
73
A mask is a 32-bit number corresponding to an IP address. The number consists of
1s and 0s. Principally, these 1s and 0s can be combined randomly. However, the
first consecutive bits are set to 1s when you design a mask. The mask divides the IP
address into two parts: subnet address and host address. The part of IP address
that corresponds to the bits 1s in the mask indicates the subnet address and the
other part of IP address indicate the host address. If there is no subnet division,
then its subnet mask is the default value and the length of "1" indicates the net-id
length. Therefore, for IP addresses of classes A, B and C, the default values of
corresponding subnet mask are 255.0.0.0, 255.255.0.0 and 255.255.255.0
respectively.
1s and 0s. Principally, these 1s and 0s can be combined randomly. However, the
first consecutive bits are set to 1s when you design a mask. The mask divides the IP
address into two parts: subnet address and host address. The part of IP address
that corresponds to the bits 1s in the mask indicates the subnet address and the
other part of IP address indicate the host address. If there is no subnet division,
then its subnet mask is the default value and the length of "1" indicates the net-id
length. Therefore, for IP addresses of classes A, B and C, the default values of
corresponding subnet mask are 255.0.0.0, 255.255.0.0 and 255.255.255.0
respectively.
The mask can be used to divide a Class A network containing more than
16,000,000 hosts or a Class B network containing more than 60,000 hosts into
multiple small networks. Each small network is called a subnet. For example, for
the Class B network address 138.38.0.0, the mask 255.255.224.0 can be used to
divide the network into eight subnets: 138.38.0.0, 138.38.32.0, 138.38.64.0,
138.38.96.0, 138.38.128.0, 138.38.160.0, 138.38.192.0 and 138.38.224.0
(Refer to the following figure). Each subnet can contain more than 8000 hosts.
16,000,000 hosts or a Class B network containing more than 60,000 hosts into
multiple small networks. Each small network is called a subnet. For example, for
the Class B network address 138.38.0.0, the mask 255.255.224.0 can be used to
divide the network into eight subnets: 138.38.0.0, 138.38.32.0, 138.38.64.0,
138.38.96.0, 138.38.128.0, 138.38.160.0, 138.38.192.0 and 138.38.224.0
(Refer to the following figure). Each subnet can contain more than 8000 hosts.
Figure 15 Subnet division of an IP address
Configuring IP
Address
Address
The following sections describe IP address configuration tasks:
■
■
■
■
Configuring the
Hostname and Host IP
Address
Using this command, you can associate a host name with an IP address. After that,
when using an application like telnet, you can use the host name instead of the IP
address that is hard to memorize, and the system automatically translates the host
name to the IP address.
when using an application like telnet, you can use the host name instead of the IP
address that is hard to memorize, and the system automatically translates the host
name to the IP address.
Perform the following configuration in system view.
10001010, 00100110, 000 00000, 00000000
ClassB
138.38.0.0
Subnet mask
255.255.224.0
11111111, 11111111, 111 00000, 00000000
11111111, 11111111, 000 00000, 00000000
Standard
mask
mask
255.255.0.0
Subnet address:
000
Subnet address: 138.38. 0. 0
001
Subnet address: 138.38. 32. 0
010
Subnet address: 138.38. 64. 0
011
Subnet address: 138.38. 96. 0
100
Subnet address: 138.38.128. 0
101
Subnet address: 138.38.160. 0
110
Subnet address: 138.38.192. 0
111
Subnet address: 138.38.224. 0
Subnet
number
number
Host
number
number
Subnet address: