IP Summary Route Calculator: Optimizing BGP Tables

In IP routing, route aggregation, also known as route summarization, is a technique used to reduce the number of routing table entries by grouping multiple routes into a single summary route. This approach can significantly optimize the Border Gateway Protocol (BGP) tables in network devices.

In this article, we will explore how to use an IP summary route calculator to create a 172.16.0.0/21 summary route that includes all more-specific routes without any overlap. We will demonstrate how to implement aggregation at R3 to optimize the BGP table on R4.

To begin, let's inspect the BGP table on R4. The output shows four routes each from AS 10 and 20. This indicates that maintaining eight independent routes is unnecessary, as R4 only has a single path to all of these subnets.

```

Network Next Hop Metric LocPrf Weight Path

Origin codes: i - IGP, e - EGP, ? - incomplete

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

```

The `aggregate-address` command can be used on R3 to generate a summary route. By implementing aggregation at R3, we can reduce the number of routes in the BGP table on R4.

In our sample lab, routers one and two each advertise four /24 routes to their respective networks. To achieve this level of flexibility, route aggregation with BGP is extremely flexible, but this also leads to difficulty remembering all the different tweaks that can be used to manipulate aggregate routes.

Let's break down the configuration parameters for aggregation and explore how each can influence the advertisement of an aggregate route:

* `summary-only`: This command specifies whether the aggregate route should only be advertised as a summary or not.

* `suppress-map`: This command is used to suppress specific routes within the aggregate.

* `advertise-map`: This command is used to advertise specific routes within the aggregate.

By understanding these configuration parameters and how they can be used, network administrators can effectively optimize their BGP tables using IP summary route calculators.

Ip summary route calculator