Classful network 2

[tiffyhoolz]

Please could someone tell me exactly & concisely the definition of a "classful network" (NOT the definition of "classful addressing", "subnetting" or anything else!). Thanks.

 

[burtsbees]

A classful network is simply a network that is not subnetted---the "default" netmask is used. Sorry for the "s" word, but here it is again. A subnet mask is actually a netmask for a subnet. So 192.168.1.0 without being subnetted will have a netmask of 255.255.255.0, NOT a subnet mask.

Burt

 

[johnny99]

I would add that you use the old type of networks. Class-A, Class-B, Class-C (and D and E) networks.

Class Start End CIDR subnet mask
Class A 0.0.0.0 127.255.255.255 /8 255.0.0.0
Class B 128.0.0.0 191.255.255.255 /16 255.255.0.0
Class C 192.0.0.0 223.255.255.255 /24 255.255.255.0
Class D 224.0.0.0 239.255.255.255 /4
Class E 240.0.0.0 255.255.255.255 /4

So using 10.1.0.0 with a netmask of 255.255.0.0 would not be classful but 172.16.0.0 with a netmask of 255.255.0.0 would be classful

/johnny

 

[burtsbees]

But 0.0.0.0 is NOT class A---it represents "any" IP address...A starts at 1.1.1.1, but good explanation.

Burt

 

[johnny99]

As I understand it 0.0.0.0/8 is an class-A address, but as stated in RFC3330 is is a special network (eg like 127.0.0.0/8)

And by your description the first class-A nwtwork would not start at 1.1.1.1 but 1.0.0.0/8
1.0.0.1 would be a valid host address in 1.0.0.0/8

But for any practical use we do agree.

/johnny