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H3C S7500 Series Ethernet Switches Operation Manual

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Operation Manual – IP Address-IP Performance-IPX
H3C S7500 Series Ethernet Switches Chapter 1
IP Address Configuration
1-3
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. A 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 an
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 8,000 hosts.
10001010, 00100110, 000 00000, 000000
ClassB
138.38.0.0
Subnet mask
255.255.224.0
00
11111111, 11111111, 111 00000, 00000000
11111111, 11111111, 000 00000, 000000
Standard
mask
255.255.0.0
Subnet address:
00
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
Host
numb
er
Subnet address:
10001010, 00100110, 000 00000, 000000
ClassB
138.38.0.0
Subnet mask
255.255.224.0
00
11111111, 11111111, 111 00000, 00000000
11111111, 11111111, 000 00000, 000000
Standard
mask
255.255.0.0
Subnet address:
00
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
Host
numb
er
Subnet address:
10001010, 00100110, 000 00000, 000000
ClassB
138.38.0.0
Subnet mask
255.255.224.0
00
11111111, 11111111, 111 00000, 00000000
11111111, 11111111, 000 00000, 000000
Standard
mask
255.255.0.0
Subnet address:
00
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
Host
numb
er
Subnet address:
10001010, 00100110, 000 00000, 000000
ClassB
138.38.0.0
Subnet mask
255.255.224.0
00
11111111, 11111111, 111 00000, 00000000
11111111, 11111111, 000 00000, 000000
Standard
mask
255.255.0.0
Subnet address:
00
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
Host
numb
er
11111111, 11111111, 111 00000, 00000000
11111111, 11111111, 000 00000, 000000
Standard
mask
255.255.0.0
Subnet address:
00
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
Host
numb
er
Subnet address:
Figure 1-2 Subnet division of the IP address
1.2 Configuring IP Address(es) for a VLAN Interface
You can only configure an IP address for the VLAN interface using a corresponding
command. Generally, it is enough to configure one IP address for a VLAN interface.