IPv4 Subnet Calculator

This calculator and tool allows you to type an IP address in and get information on a particular subnet. Enter an IP or range in CIDR notation.

Network: 21.0.3.138/31
Addresses: 2 (2¹)
First IP: 21.0.3.138 (138.3.0.21.in-addr.arpa)
Last IP: 21.0.3.139 (139.3.0.21.in-addr.arpa)

/8 Operated By: DDN-RVN

Related Networks

21.0.0.0/8
20.0.0.0/8
22.0.0.0/8
21.0.3.136/30
21.0.3.138/32
21.0.3.139/32

You can also use some of the other examples such as:

0.0.0.0/0
1.0.0.0/8
127.0.0.1
30.0.0.0/8
192.168.0.0/16