Classful vs Classless

fusebox

Could someone explain this to me in their own words...?

I somewhat understand it. I know that RIP v1 and IGRP use classful routing, and RIPv2, EIGRP, OSPF use classless routing.

Am I right in saying that with classful routing, the whole network would come under a certain subnet mask, where as if using classless routing, some links in the network can have differnet subnet masks, and some links can use different subnet masks?

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TranscenderMichael

In basic terms, yes.

Classful routing protocols do not send any subnet mask information in their routing updates. They assume that the mask that should be used is the full classful subnet mask (Class A - 255.0.0.0, Class C - 255.255.255.0, etc).

Classless routing protocols DO send subnet mask information within routing updates. They don't assume that just because you've got a Class B address that you're using the entire range.

tunerX

A classful protocol does not send subnet information but it will send the complete network address. The router will supply its own subnet mask based on its locally configured subnets. As long as you have the same subnet mask and the network is contiguous, you can use subnets of a classful network address.

The only problem with this is that if you want to support subnets then you have to make sure that the entire network is contiguous across all routers and interfaces in that network range.

A classful protocol sends subnet information. This allows you to create discontiguous networks with any given classful network address.