1

As I understand, subnet mask must be contiguous. So e.g. you can't have a mask of 255.1.0.0. The networks are often denoted as e.g. 192.168.5.0/24, which automatically contains all the information to derive the subnet mask, and with such a derivation it is guaranteed to be contiguous.

Why do the users have to manually "expand" this number 24 into 255.255.255.0 instead of simply entering the number 24 into network configuration? Is there any case where subnet mask would be required and the number of 1-bits in the mask not sufficient for configuration?

Ruslan
  • 1,720

1 Answers1

0

It is simply software dependant.

When the RFC's are written up, they generally won't define how a value is presented to a end user, only how it 'works'. So you end up with the effect you've seen where different programs implement the same number in different ways.

The same subnet presented in different ways:

  • 255.255.255.0
  • /24
  • 11111111.11111111.11111111.00000000

The same can be seen with the presentation of mac addresses:

  • Cisco formats in IOS: FFFF.FFFF.FFFF
  • Microsoft cli does: FF-FF-FF-FF-FF-FF
  • Microsoft DHCP: FFFFFFFFFFFF
  • Most network card manufcturers: FF:FF:FF:FF:FF:FF

These all represent the same mac address, just in different forms.

djsmiley2kStaysInside
  • 6,943
  • 2
  • 36
  • 48