22 – BGP Aggregation Address 6,520 views

Posted by Mo7sin in CCNP, CCNP Routing (642 - 902) On 15/05/2012 at 12:16 AM

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:

Components Used

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.

Network Diagram


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.

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