Route Summarization

There are some features of a network that can be confusing, and some may say that route summarization can be a difficult concept to grasp. Read on for a breakdown of what route summarization is, its benefits, and other key information that will aid in the understanding of this process.

An Overview of Route Summarization
You may have heard of route summarization before, even if the term doesn’t sound familiar. This is because this process goes by other names including supernetting, aggregate address, route summarization, and summary address.

In short, though, route summarization means that a group of networks is consolidated into one network. The primary objective is to reduce the complexity and routing table size. The most common summarization is the RFC1918 Class B Range, which has a range of – The route summarization for this range is which, as you can see, reduces the complexity.

What Is Route Summarization Used For?
With a range of IP addresses, each individual address adds to the routing table, which in turn uses up more memory. With route summarization, the consolidated address reduces memory requirements.

How to Summarize
The concept of summarizing can seem confusing in and of itself, and this can get even more complex when trying to actually perform the task of summarizing. However, this can be done with a few simple steps.

The first step is to identify the first octet with a change of address. Once this has been identified, write out the binary equivalents of every octet leading up to that change, as well as include the changed octet in your calculations.

Starting from the left, count the number of bits that are the same in the range of addresses. This will provide you with your mask in slash notation. For example, if your first address is and the first 12 bits are the same, this would be written as This is your summarization.

Final Thoughts
Route summarization doesn’t have to be a complex process, but there are a lot of elements involved. You may encounter some challenges not outlined here, as well. Do you have any questions about route summarization? Do you have a tip, trick, or story to share about this process? Then comment below!


CCNA Prep: Route Summarization—A Need for a Routing Table