topic Subnet mask in Operating System - Linux

Subnet mask

Ragni Singh — Fri, 07 Apr 2006 18:58:11 GMT

Hello, what would be the subnet mask of this ip address..

216.239.114.0/24

Thanks and points will be assigned.

Re: Subnet mask

Stuart Browne — Fri, 07 Apr 2006 23:24:50 GMT

The '/24' at the end states that the subnet mask is already set using CIDR. But to expand it, the '/24' equates to '/255.255.255.0'.

So this value means anything from 216.239.114.0-216.239.114.255 .

Re: Subnet mask

Ajay Agarwal — Sat, 08 Apr 2006 01:50:27 GMT

Sanjit,

In this case subnet mask is 255.255.255.0.

-Ajay

Re: Subnet mask

Thomas Ries — Sun, 09 Apr 2006 03:52:48 GMT

You can use the ipcalc utility to do
various "calculations" related to IP addresses:

$ ipcalc --usage
Usage: ipcalc [-bhmnps?] [-b|--broadcast] [-h|--hostname] [-m|--netmask]
[-n|--network] [-p|--prefix] [-s|--silent] [-?|--help] [--usage]

example netmask:
$ ipcalc -m 216.239.114.0/24
NETMASK=255.255.255.0

accordingly the broadcast address:
$ ipcalc -b 216.239.114.0/24
BROADCAST=216.239.114.255

Regards,
/Thomas

Re: Subnet mask

Sivakumar TS — Mon, 10 Apr 2006 05:06:18 GMT

Hi,

use this smart tool...

http://jodies.de/ipcalc

it is web based and works good...

Hope this is useful

Siva.

Re: Subnet mask

Ivan Ferreira — Mon, 10 Apr 2006 08:15:49 GMT

The subnet mask is a binary value, translated to decimal. The subnet mask is 8 octets, like this:

11111111.11111111.11111111.00000000

When all octects are 1, the value is 255, when all 0 is 0, a simple binary to decimal conversion.

So, when you say /24, you are saying that you have 24 subnet mask bit to 1, that would be translated to 255.255.255.0, if you say /16, that means 2 octets to 1, giving 255.255.0.0, and /8 would be:

11111111.00000000.00000000.00000000

Or 255.0.0.0.

This is very simple, but this can be more complex if you use a subnet mask like 255.255.252.0. It worth to learn what this does.