Technical Documentation

Configuring Aggregate Addresses

As the number of BGP router addresses grows, each route in the AS requires more memory and CPU time to process addresses from the routing table. Using aggregation, BGP can reduce the size of a routing table by summarizing a range of addresses into a single route entry. Each address range included in the aggregate address is considered a contributing route within the aggregate address.

For each aggregate address you want to use, create an aggregate address entry that contains the aggregate address IP and netmask. Next, configure the route attributes for the address. The aggregate address configuration details are displayed in Table 1.

Table 1: Aggregate Address

Parameters

Your Action

AS Set

When enabled, BGP generates AS set-path information for the aggregated route and all contributing routes.

Summary Only

When enabled, BGP advertises the aggregate route in place of individual addresses for more specific contributing routes. If you select this option, you cannot configure a Suppress Route Map entry for this aggregate route.

Route Maps (ScreenOS 5.1 and later only)

Configure a previously created route map for each of the following:

  • Advertise Route Map—Select the previously created route map that defines the path attributes for the aggregate route.
  • Attribute Route Map—Select the previously created route map that defines the route attributes for the aggregate route.
  • Suppress Route Map—Select the previously created route map that you want BGP to suppress for the aggregate route. If you select this option, you cannot enable Summary Only for this aggregate route.

Published: 2009-08-20