BGP Route Aggregation and Route Summarization

BGP route aggregation and route summarization are key techniques used to optimize the routing process in large networks. Route aggregation involves combining multiple specific IP routes into a single, broader route, reducing the number of routes that need to be advertised and maintained.

In this article, we are going to discuss BGP in detail along with proper diagrams and explanations.

Autonomous System (AS) is the basic unit of routing, and BGP is the specific routing protocol used to exchange routing information between two distinct ASes on the Internet. Thus, one of the significant developments in BGP for the management of the size of the routing table as well as for the improvement of the network efficiency is the route aggregation and route summarization. These techniques help to minimize the number of routes that need to be advertised and in return those that need to be maintained hence leading to a scalable and qualitative network.

• BGP (Border Gateway Protocol): Constructed in 1995 to take the place of the initial details NAPs, Border Gateway Protocol or BGP is a standardized exterior gateway protocol that can conveniently facilitate switching routing and reachability information amid diverse autonomous systems (ASes) of the internet.
• Autonomous System (AS): A collection of interconnected IP networks together with its routers which comprises one network out of authority of a single administration addressing the problem or issues of the internet effectively.
• Route Aggregation: This is the operation by which information coming from a group of IP prefixes in a certain portion of a network, is consolidated into a single, more inclusive IP prefix. This prevents the large routing table from forming, as we saw earlier explained above.
• Route summarization: This is done in the same way as in the case of Route aggregation where the summary of the routesome is presented as several routes. This makes sense within an AS with the intent of reducing confusion as to what information constitutes the input to the AS.
• Prefix: The two common components are an IP number, and a subnet mask that refers to the sequence of IP addresses.

1. Identify the Routes to Aggregate

The various routes through which B2B‘s online aggregators are available are as follows.

2. Calculate the Summary Route

However, following the usual route summarization method, where the ‘1s’ are aligning, the summary of the given IP prefixes are as follows:For example, the prefixes 192.168.1.0/24 and 192.168.2.0/24 can be summarized to 192.168.0.0/22.

3. Advertise the Summary Route

It also means it is more efficient to tell other routers about an area where the summarized route can be found rather than telling them about the specific routes to another router destination.

4. Update the Routing Table

In this case there should be an entry of the summarized route within every router for the purpose of reducing total routing table entries so that the routings can be eased.

We have three subnets in an System :

1. Subnet A: 192.168.1.0/24
2. Subnet B: 192.168.2.0/24
3. Subnet C: 192.168.3.0/24

These subnetworks can be:

• Summary Route: 192.168.0.0/22
• Aggregated Summary Route (192.168.0.0/22)

BGP route aggregation and route summarization are techniques that must be embraced by any organization largely due to their effectiveness in managing today’s complex large networks. These methods create more efficiency in the network, improves routing performance and ease network management by minimizing the number of routes that is being held in the routing table. It is only possible when there is knowledge of these innovations, which help the coordinators of network management to regulate the data flow in separate AS, creating effective mechanisms for routing. When route aggregation/summaries are used appropriately, not only does it save such resources but also aids in making the Internet much more stable and easily expandable.

What is the most important benefit obtained by route aggregation in BGP?

In our case the most crucial benefit that can be derived out of the implementation of route aggregation in BGP is the impact towards the reduced sizes of the routing table so as to get more scaling factors in the network.

Route aggregation in general, can it result to routing loops?

When done wrongly, the following dangers might be observed to occur, and this might prove rather unfortunate for a network; Routing circles. Nevertheless, non-specific carelessness and absence of adoption and supervision can be regarded as the major factors which lead to such issues.

What can be said about more specifically defining routing summarization and routing aggregation?

There is the internal route summarization that is useful in reducing the number of internal prefixes within the same AS, and there is the external route summarization whereby the number of prefixes to be advertised to a neighbor is limited. In laymans terms both of them converge for the purpose of reducing the number of entries in the routing tables.