Matching Address Classes with Prefix-Lists (Followup)

This article is a follow up on the Matching Address Classes with Prefix-Lists based on the comments from killerkadoogan. I think its easier to answer the comments this way, I hope you don’t mind

Hi Pashtuk,

Under the technical definition of a CLASS C network, IE using classes. 192.168.0.0/16 is NOT a class C network. So ‘Class C: 192.0.0.0/3 le 32′ would also block or allow that ‘supernet’ of Class C’s, which isn’t a Class C in itself. Old-school routers (ie RIPv1) would convert the mask to /24,Class C is technically:
bits 1-3 110 + a 24 bit mask.

Cheers,KK

check out http://www.ietf.org/rfc/rfc791.txt“in class c, the high order three bits are one-one-zero, the next 21 bits are the network and the last 8 bits are the local address.”so the technically correct Class C prefix list is:
192.0.0.0/3 ge 24 le 24

you wouldn’t use that in the real world though 

You are right if we are talking about the old “classical” concept of Address Classes with their definition of the subnet mask.

Nonetheless the classical concept does not really matter much anymore nowadays, even though the terms Class A/B/C are still in use. Most of the time if we talk about a Class C network today a /24 subnet is thought off, no matter to which original Class the subnet belongs too.

On another occasion we can also talk about Classes in the meaning of ranges grouped into those defined classes (as used in the article).  In that case, it doesn’t matter what the typical subnet mask was, it only matters that we are able to match every subnet out of that range no matter which mask it got.

It does not have much to do with a real world approach, as a lot of the CCIE stuff I had to learn, but it belongs into the stuff a person has to know for the CCIE lab.