More in TCP/IP and Subnet Mask Calculator

Some special IP addresses

localhost 127.0.0.1 (loopback address)
local IP numbers
- Class A 10.0.0.0
- Class B 172.16.0.0 to 172.31.0.0
- Class C 192.168.0.0 to 192.168.255.0
Machines behind a firewall or NAT (Network Address Translator) server can use these IP numbers to communicate among them
Only the firewall of the NAT Server needs to have a valid IP number
The NAT server keeps tables of connections from local IP numbers to valid Internet IP numbers and manage their communications.

Subnet Mask calculator

We have seen an introduction to Subnet Mask calculations previously. Lets see an example to make the use of the IP calculator easier to understand. We decided to use 192.168.3.0 as our basic C address and we want to have eight(8) subnets. If we consult the table seen previously for eight subnets the number of bits to enter in the IP calculator is 3, as shown in the next image.

The IP calculator displayed the subnet mask and the IP numbers in each subnet, including the subnet address and broadcast address. It does not tell you the IP number of the default gateway, but we know that the first IP number of a subnet is the IP number of the default gateway, therefore 192.168.3.1 and 192.168.3.33 are the default gateway addresses for respectively subnet 0 and subnet 1.

This page is maintained by Al Bento who can be reached at . This page was updated on October 8, 2011. Although we will attempt to keep this information accurate, we can not guarantee the accuracy of the information provided.