How to calculate the subnet number

Subnet number calculation is used to divide the network into subnetworks. The specific steps include: 1. Determine the subnet mask, such as 255.255.255.0, which specifies the network number and host number; 2. Calculate the network number, For example, 192.168.1.0 is obtained by ANDing the IP address with the subnet mask; 3. Calculate the subnet number, such as 192.168.1.64, by adding extra bits to subdivide the network; 4. Calculate the subnet broadcast address, such as 192.168.1.127, obtained by setting the host number bit in the subnet number to 1.

Subnet number calculation

The role of the subnet number is to divide a large network into multiple smaller ones subnetworks, each subnetwork has its own independent address space. The calculation of the subnet number requires the following steps:

1. Determine the subnet mask

The subnet mask is used to combine the network number and host number in the IP address separate. It is a 32-bit binary number, in which the network number part is 1 and the host number part is 0. For example, for the subnet mask 255.255.255.0, the network number is 24 bits and the host number is 8 bits.

2. Calculate the network number

The network number is the bit that belongs to the network part of the IP address. It can be obtained by ANDing the IP address with the subnet mask. For example, if the IP address is 192.168.1.1 and the subnet mask is 255.255.255.0, the network number is 192.168.1.0.

3. Calculate the subnet number

The subnet number is the extra bits after the network number that are used to further subdivide the network. The number of digits in the subnet number is determined by the number of digits in the host number in the subnet mask. For example, for the subnet mask 255.255.255.0, the host number is 8 bits, so 2^8 = 256 subnets can be created.

4. Calculate the subnet broadcast address

The subnet broadcast address is a special address in the subnet that allows messages to be sent to all hosts. It can be obtained by setting all host number bits in the subnet number to 1. For example, for the subnet number 192.168.1.0, the subnet broadcast address is 192.168.1.255.

Example:

To calculate the subnet number of IP address 192.168.1.100 in subnet mask 255.255.255.128, please perform the following steps:

• Network number: 192.168.1.0 (AND operation of IP address and subnet mask)
• Number of host number digits: 7 (minus the 25 network number digits in the 32-bit subnet mask) 8 host number digits)
• Subnet number: 192.168.1.64 (Add 7 digits of 0 after the network number, then 1)
• Subnet broadcast address: 192.168.1.127 (Subnet number The host number bits in all are set to 1)

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