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: 21.255.128.0/17
Addresses: 32768 (2¹⁵)
First IP: 21.255.128.0 (0.128.255.21.in-addr.arpa)
Last IP: 21.255.255.255 (255.255.255.21.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
21.255.0.0/16
21.255.128.0/32
21.255.255.255/32

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