Subnet And Mask; Configuring An Ip Address - Huawei Quidway S3900 Series Operation Manual

Operation Manual – IP Address and Performance Confiugration
Quidway S3900 Series Ethernet Switches-Release 1510

1.1.2 Subnet and Mask

The traditional IP address classification method wastes IP addresses greatly. In
order to make full use of the available IP addresses, the concepts of mask and
subnet were introduced.
A mask is a 32-bit number corresponding to an IP address. The number consists of
1s and 0s. An mask is defined as follows: the bits of the network number and
subnet number are set to 1, and the bits of the host number are set to 0. The mask
divides the IP address into two parts: subnet address and host address. In an IP
address, the part corresponding to the "1" bits in the mask is the subnet address,
and the part corresponding to the remaining "0" bits in the mask is the host
address. If there is no subnet division, the subnet mask uses the default value and
the length of 1s in the mask is equal to the net-id length. Therefore, for IP
addresses of classes A, B and C, the default values of the corresponding subnet
masks 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 (see
Figure 1-2). Each subnet can contain more than 8000 hosts.
ClassB ClassB ClassB ClassB ClassB ClassB
138.38.0.0 138.38.0.0 138.38.0.0 138.38.0.0 138.38.0.0 138.38.0.0
Standard Standard Standard Standard Standard Standard
mask mask mask mask mask mask
255.255.0.0 255.255.0.0 255.255.0.0 255.255.0.0 255.255.0.0 255.255.0.0
Subnet m ask Subnet m ask Subnet m ask Subnet m ask Subnet m ask Subnet m ask
255.255.224.0 255.255.224.0 255.255.224.0 255.255.224.0 255.255.224.0 255.255.224.0
Subnet address: Subnet address: Subnet address: Subnet address: Subnet address: Subnet address: Subnet address: Subnet address: Subnet address: Subnet address: Subnet address:
000 000 000 000 000 000
001 001 001 001 001 001
010 010 010 010 010 010
011 011 011 011 011 011
100 100 100 100 100 100
101 101 101 101 101 101
110 110 110 110 110 110
111 111 111 111 111 111
Figure 1-2 Subnet division of the IP address

1.2 Configuring an IP Address

For a VLAN interface, an IP address can be obtained in one of the three ways:
Manually configured by using the IP address configuration command
10001010, 00100110, 000 00000, 00000000 10001010, 00100110, 000 00000, 00000000 10001010, 00100110, 000 00000, 00000000 10001010, 00100110, 000 00000, 00000000 10001010, 00100110, 000 00000, 00000000 10001010, 00100110, 000 00000, 00000000
11111111, 11111111, 000 00000, 00000000 11111111, 11111111, 000 00000, 00000000 11111111, 11111111, 000 00000, 00000000 11111111, 11111111, 000 00000, 00000000 11111111, 11111111, 000 00000, 00000000 11111111, 11111111, 000 00000, 00000000
11111111, 11111111, 111 00000, 00000000 11111111, 11111111, 111 00000, 00000000 11111111, 11111111, 111 00000, 00000000 11111111, 11111111, 111 00000, 00000000 11111111, 11111111, 111 00000, 00000000 11111111, 11111111, 111 00000, 00000000
Subnet address: 138.38. Subnet address: 138.38. Subnet address: 138.38. Subnet address: 138.38. Subnet address: 138.38. Subnet address: 138.38. 0. 0. 0. 0. 0. 0.
Subnet address: 138.38. 32. Subnet address: 138.38. 32. Subnet address: 138.38. 32. Subnet address: 138.38. 32. Subnet address: 138.38. 32. Subnet address: 138.38. 32.
Subnet address: 138.38. 64. Subnet address: 138.38. 64. Subnet address: 138.38. 64. Subnet address: 138.38. 64. Subnet address: 138.38. 64. Subnet address: 138.38. 64.
Subnet address: 138.38. 96. Subnet address: 138.38. 96. Subnet address: 138.38. 96. Subnet address: 138.38. 96. Subnet address: 138.38. 96. Subnet address: 138.38. 96.
Subnet address: 138.38.128. Subnet address: 138.38.128. Subnet address: 138.38.128. Subnet address: 138.38.128. Subnet address: 138.38.128. Subnet address: 138.38.128.
Subnet address: 138.38.160. Subnet address: 138.38.160. Subnet address: 138.38.160. Subnet address: 138.38.160. Subnet address: 138.38.160. Subnet address: 138.38.160.
Subnet address: 138.38.192. Subnet address: 138.38.192. Subnet address: 138.38.192. Subnet address: 138.38.192. Subnet address: 138.38.192. Subnet address: 138.38.192.
Subnet address: 138.38.224. Subnet address: 138.38.224. Subnet address: 138.38.224. Subnet address: 138.38.224. Subnet address: 138.38.224. Subnet address: 138.38.224.
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1-3
Chapter 1 IP Address Configuration
Subnet Subnet Subnet Subnet Subnet Subnet Host Host Host Host Host Host
number number number number number number
number number number number number number
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0