Find the number of subnets for a network

Subnetting is the process of diving a network into small networks and is a common task on IPV4 networks.

example: 192.168.0.25/29

/29 -> 11111111.11111111.11111111.11111000

Take the octect where there is the split between 0 and 1 -> 11111000. Count the number of bits (1), int the example there is 5 bits that are used to identify the subnet. To find the total number of subnets available simply raise 2 to the power of 5 like that: 2^5 = 32. The number of subnet is 32.

Find the number of host addresses for a network

The total number of IPv4 host addresses for a network is 2 to the power of the number of host bits, which is 32 minus the number of network bits.

example: 192.168.0.25/29

Do 32 minus the mask of the network the whole squared minus 2 like that: ((32-29)^2)-2 = 6. The number of hosts is 6.

Find the broadcast address of a network

In computer networking, broadcasting refers to transmitting a packet that will be received by every device on the network. In practice, the scope of the broadcast is limited to a broadcast domain.

example: 192.168.0.133/29

/29 -> 11111111.11111111.11111111.11111000 Take the octect where there is the split between 0 and 1 -> 11111000 and complement to 1 -> 00000111.

133 –> 10000101
/29 –> 00000111 complemented to 1
----------------
binary or 10000111

The broadcast is 10000111, 192.168.0.135/29.

Find network address / NETID

A network address is an identifier for a node or host on a telecommunications network.

example: 173.115.163.86/20

163 –> 10100011
163 –> 1010|0011cutting

Take the left part 1010 -> 160

  • The network address is 173.115.160.0/20.
  • The first network address is 173.115.160.1/20.

Find the last possible address of a network

example: 173.115.163.86/20 network address: 173.115.160.0/20

1010|1111.11111111 remplace the right paty by one
1010|1111.11111111 -> 175.255

  • The broadcast address is 173.115.175.255/20.
  • The last possible address is 173.115.175.254/20