Classful Auto Summarization – RIPv1

Consider the following network

Both Router TK1 and Router TK2 are running RIPv1. Both routers are configured to
advertise all of their attached networks via RIP. Router TK1 will only see a router advertised from by Router TK2. This decision process is based on RIPv1s auto summarization.

Rule 1 – Subnet
This subnet is dropped because Router TK2 compares the mask to its other subnet and they do not match.

For interfaces that are part of the same major network (ie in this case) all the component networks should have the same subnet mask. The only change is if the interface is a /32 (or host route).

Rule 2 – Subnet
This subnet is dropped because this route is a super net (ie /22 mask rather than a bunch of /24). Advertising any network prefix less than its classful major network is not allowed in RIP route summarization.

Rule 3 – Subnet
This route isn’t part of a major network the router knows about so Rule 1 does not apply. This subnet is also not a super net of a classful network so Rule 2 does not apply. As a result this route is summarize to its classful boundary and send it out to Router Tk1


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s