Question

So, I’ve been looking on different websites, and using different subnet calculators, where in some cases it’s possible and others it isn’t possible.

Are these IPs possible?

Class A: 11.66.12.49/6 (Less than 8 network bits)

Class B: 133.22.15.1/10 (Less than 16 net bits)

Class C: 201.2.115.25/18 (Less than 24 net bits)

Sources:

http://jodies.de/ipcalc?host=201.2.115.25&mask1=18&mask2=

http://www.subnet-calculator.com/subnet.php?net_class=C

So basically, can you have a class C IP address with 5 netbits? or a class B for that matter?

Answer 1

Yes, it is possible.

Basically, the classes are the IP address ranges:

  - Class A: 0.0.0.0 - 126.255.255.255
  - Class B: 128.0.0.0 - 191.255.255.255
  - Class C: 192.0.0.0 - 223.255.255.255
  - Class E: ...
  - Class F: ...

With that said, if your in a classful network, you have to use the default subnet masks: /8 – /16 – /24.

On the other hand, if your in a classless network, you may use any subnet mask, no matter the value of the first octet.

Hope this helps!

Sources:

• [Classless Networks] http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing
• [Classful Networks] http://en.wikipedia.org/wiki/Classful_network