CODEWITHSUNDEEP
routesipsubnet
Bober02
Bober02

Reputation: 15341

Subnet masks and routing protocols

I have a probably very simple question, but I am getting confused about the general notion of subnet masks and their use in different routing protocols.

While I understand the basic use-case for subnet masks, I would like to know whether all routing algorithms (both exterior and interior) make use of subnet part of IP address when routing or not? If there is a distinction, could you prvide an example and state why a certain protocol does not use it?

Upvotes: 0

Views: 891

Answers (1)

Joël Salamin
Joël Salamin

Reputation: 3576

First of all, here are an illustration of the TCP/IP Model (it may help to identify the layer that is concerned by the routing protocols) :

TCP/IP Model

If you know the general notion, you probably have at least heard of the OSI Model that is the theoretical model dividing the network into 7 layers. The TCP/IP Model is an implementation of the OSI Model. Here is an illustration to better understand the differences between both models:

enter image description here

As you can see on the TCP/IP Model, the routing protocols are part of the Internet Layer (same layer as the Internet Protocols).

Now that we know exactly where we are in the model, we can focus on the routing protocols. These protocols can be classified in different manner and there is a classification that perfectly matches your need: Behavior (Classful or Classless).

The biggest difference between classful and classless routing protocols is that classless routing protocols include subnet mask in the routing updates, classful protocols don't. Classfull protocols (RIPv1 and IGRP) are legacy protocols and they are only used in older networks, these protocols into RIPv2 and EIGRP that are classless protocols.

You'll find all information about these classifications and the routing protocols here: Type of Routing Protocols And here is a short article that describes how these routing protocols operate in routing: Classless and Classful Routing

And here is another link with a much more technical approach if you're interesting in learning more details about how it works: Classful vs Classless Protocols

To close this post, i just want to add a link to a very interesting website that describe the notion of subnets (in order to make the post as complete as possible to help every interested users): Internet Protocol Subnet

Hope this will help you and that i answered your question ;-)

Upvotes: 5

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