How to calculate create table of Subnets addresses, range of Hosts and Broadcast

Create a table with the subnet addresses, valid host address range, and the subnet's Broadcast address.

A certain organization received from the IP address regulatory authority the address, to be used in its internal network, but for various reasons, the company needs 6 subnetworks, with 30 hosts (computers) in each subnetwork.

How to solve this problem?

1st Find out which class belongs to the IP range.

First you need to find out which class this IP range belongs to, see more about IP Protocol Classes at

IP ranges 192 to 223 belong to Class C, therefore IP is Class C.

The default Class C IPs Subnet Mask is, i.e Host.Host.Host.Net. So the default Subnet Mask of IP is

2nd Create a Subnet and Host table

In IP Mask I have the last octet to form the subnet list and the host list. I say Octet because the IP or Mask numbers in binaries correspond to:

  • (decimal) = 11111111.11111111.11111111.00000000 (binary) cannot be used as it is the network address and cannot be used as it is the Broadcast address. What was left was the range from to, from these numbers I need to create the subnet and the list of hosts.

  • If I use 1 bit for subnetting (1000000) I will have 2 left7-2 for host list
  • So we will have 21-2 for subnet address and 27-2 for host list
  • That is, a list of 2-2* addresses to the subnet and a list of 128-2* addresses to hosts.

NOTE: O * represents the first and last address that is reserved for the Main Subnet and for Broadcast. These addresses cannot be used.

A list follows.

lista sub-redes e hosts
subnets and hosts list

According to the list above, only option C fits the criterion of 06 subnets with 30 hosts each.

3rd Create the list with the Subnet and Hosts ranges for each Subnet


  1. Subnet 000 00000 = The Subnet 000 11111
  2. Subnet 001 00000 = The Subnet 000 11111
  3. Subnet 010 00000 = The Subnet 000 11111
  4. 011 subnet 00000 = The Subnet 000 11111
  5. Subnet 100 00000 = The Subnet 000 11111
  6. Subnet 101 00000 = The Subnet 000 11111
  7. Subnet 110 00000 = The Subnet 000 11111
  8. Subnet 111 00000 = The Subnet 000 11111

Host List

  1. subnet The 30 | broadcast
  2. subnet The 62 | broadcast
  3. subnet The 94 | broadcast
  4. subnet The 126 | broadcast
  5. subnet host The 158 | broadcast
  6. subnet The 190 | broadcast
  7. subnet The 222 | broadcast
  8. subnet The 254 | broadcast

That's it, we already have all the Subnet and Hosts addresses for our network.

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  1. POSTED!!!The default Class C IPs Subnet Mask is, ie Host.Host.Host.Network. So the default Subnet Mask of IP is


    There is a mistake here when you say; which is Host,Host,Host,Network,
    that the CORRECT state that it is Net,Net,Net,Host treating that the subnet mask

  2. The first three octets in the C class mask define the network! that is, it would be Rede.Rede.Rede.Hosts ; your network is and the last byte is your available hosts.

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