BGP Aggregation Introduction
Border Gateway Protocol (BGP) allows the aggregation of specific routes into one route with use of the aggregate-address address mask [as-set] [summary-only] [suppress-map map-name] [advertise-map map-name] [attribute-map map-name] command. When you issue the aggregate-address command without any arguments, there is no inheritance of the individual route attributes (such as AS_PATH or community), which causes a loss of granularity. This document illustrates how to manipulate the different attributes when you use the aggregate-address command and how to influence the propagation.
BGP Aggregation Prerequisites
BGP Aggregation Requirements
Cisco recommends that you have knowledge of these topics:
- A basic knowledge of BGP operation. Refer to BGP Case Studies.
This document is not restricted to specific software and hardware versions. However, the configuration in this document was tested with Cisco IOS® Software Release 12.2(28).
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
Refer to Cisco Technical Tips Conventions for more information on document conventions.
Aggregate Without the as-set Argument
Use of the as-set argument creates an aggregate address with a mathematical set of autonomous systems (ASs). This as-set argument summarizes the AS_PATH attributes of all the individual routes. These sample configurations enable you to examine this feature and how this argument helps BGP detect and avoid loops.Read more…