When managing a network, you will undoubtedly need to deal with subnetting. Some network administrators are able to do the binary math quite quickly in their head, to determine the subnet mask. However, others may need some help and this is where the ipcalc tool comes in handy.

Read Also: A Linux Sysadmin’s Guide to Network Management, Troubleshooting and Debugging

Ipcalc actually does a lot more – it takes an IP address and netmask and provides the resulting broadcast, network, Cisco wildcard mask, and host range. You can also use it as a teaching tool to present subnetting results in an easy to understand binary values.

Some of the uses of ipcalc are:

  • Validate IP address
  • Show calculated broadcast address
  • Display hostname determined via DNS
  • Display network address or prefix

How to install ipcalc in Linux


To install ipcalc, simply run one of the commands below, based on the Linux distribution you are using.

$ sudo apt install ipcalc 

The ipcalc package should be installed automatically under CentOS/RHEL/Fedora and it is part of the initscripts package, but if for some reason it is missing, you can install it by using:

# yum install initscripts #RHEL/CentOS
# dnf install initscripts #Fedora

How to Use ipcalc in Linux

Below you can see some examples of using ipcalc.

Get information about the network address:

# ipcalc 192.168.20.0
Sample Output
Address: 192.168.20.0 11000000.10101000.00010100. 00000000
Netmask: 255.255.255.0 = 24 11111111.11111111.11111111. 00000000
Wildcard: 0.0.0.255 00000000.00000000.00000000. 11111111
=>
Network: 192.168.20.0/24 11000000.10101000.00010100. 00000000
HostMin: 192.168.20.1 11000000.10101000.00010100. 00000001
HostMax: 192.168.20.254 11000000.10101000.00010100. 11111110
Broadcast: 192.168.20.255 11000000.10101000.00010100. 11111111
Hosts/Net: 254 Class C, Private Internet

Calculate a subnet for 192.168.20.0/24.

# ipcalc 192.168.20.0/24
Sample Output
Address: 192.168.20.0 11000000.10101000.00010100. 00000000
Netmask: 255.255.255.0 = 24 11111111.11111111.11111111. 00000000
Wildcard: 0.0.0.255 00000000.00000000.00000000. 11111111
=>
Network: 192.168.20.0/24 11000000.10101000.00010100. 00000000
HostMin: 192.168.20.1 11000000.10101000.00010100. 00000001
HostMax: 192.168.20.254 11000000.10101000.00010100. 11111110
Broadcast: 192.168.20.255 11000000.10101000.00010100. 11111111
Hosts/Net: 254 Class C, Private Internet

Calculate a single subnet with 10 hosts:

# ipcalc 192.168.20.0 -s 10
Sample Output
Address: 192.168.20.0 11000000.10101000.00010100. 00000000
Netmask: 255.255.255.0 = 24 11111111.11111111.11111111. 00000000
Wildcard: 0.0.0.255 00000000.00000000.00000000. 11111111
=>
Network: 192.168.20.0/24 11000000.10101000.00010100. 00000000
HostMin: 192.168.20.1 11000000.10101000.00010100. 00000001
HostMax: 192.168.20.254 11000000.10101000.00010100. 11111110
Broadcast: 192.168.20.255 11000000.10101000.00010100. 11111111
Hosts/Net: 254 Class C, Private Internet 1. Requested size: 10 hosts
Netmask: 255.255.255.240 = 28 11111111.11111111.11111111.1111 0000
Network: 192.168.20.0/28 11000000.10101000.00010100.0000 0000
HostMin: 192.168.20.1 11000000.10101000.00010100.0000 0001
HostMax: 192.168.20.14 11000000.10101000.00010100.0000 1110
Broadcast: 192.168.20.15 11000000.10101000.00010100.0000 1111
Hosts/Net: 14 Class C, Private Internet Needed size: 16 addresses.
Used network: 192.168.20.0/28
Unused:
192.168.20.16/28
192.168.20.32/27
192.168.20.64/26
192.168.20.128/25

If you want to suppress the binary output, you can use the -b option as shown.

# ipcalc -b 192.168.20.100
Sample Output
Address: 192.168.20.100
Netmask: 255.255.255.0 = 24
Wildcard: 0.0.0.255
=>
Network: 192.168.20.0/24
HostMin: 192.168.20.1
HostMax: 192.168.20.254
Broadcast: 192.168.20.255
Hosts/Net: 254 Class C, Private Internet

To find more about the ipcalc usage, you can use:

# ipcalc --help
# man ipcalc

You can find the official ipcalc website at http://jodies.de/ipcalc.

Conclusion

This was a simple tutorial, showing how to use ipcalc tool with some basic examples. If you have any questions or advice, make sure to submit them in the comment section below.

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