Upon completing this lesson, you will be able to use BGP peer groups to share common configuration parameters between multiple BGP peers. This ability includes being able to meet these objectives:

■ Describe the need for BGP peer groups

■ Describe the performance benefits of using BGP peer groups

■ Describe the limitations of BGP peer groups

■ Describe the characteristics of BGP peer groups when they are implemented in Cisco IOS software

■ Describe the function of the BGP Dynamic Update Peer-Groups feature

■ Describe the function of the BGP Configuration Using Peer Templates feature

■ Identify the Cisco IOS commands that are required to configure BGP peer groups

■ Identify the Cisco IOS commands that are required to monitor BGP peer groups

Peer Group Requirements

This topic describes the need for BGP peer groups.

This topic describes the need for BGP peer groups.

In many cases, a network administrator must configure a single router with a large number of neighbors, each neighbor having parameters similar to the others. This situation may cause time-consuming configuration work, because the network administrator has to configure almost the same filter-list, route-map, and prefix-list for all of the neighbors. A service provider network with an edge router having a large number of customers attached to it, where each customer requires its own BGP session, may find that all of the BGP sessions to its customer routers have almost identical configurations.

Likewise, Internal Border Gateway Protocol (IBGP) sessions are almost always identically configured. If a full mesh is deployed within an autonomous system (AS), a large number of peer configurations might exist. Recall that an AS containing only 15 routers will require ([15 * 14] / 2) = 105 neighbor sessions to meet the full-mesh requirement of BGP. Configuring 105 neighbors with duplicate parameters leads to a tremendous amount of redundant configuration.

To ease the burden of configuring a large number of neighbors with identical or similar parameters (for example, route-maps, filter-lists, or prefix-lists), the concept of peer groups was introduced. The network administrator can configure a template, or peer group. The administrator configures the peer group with all the BGP parameters that are to be applied to many BGP peers. Actual BGP neighbors are bound to the peer group, and the network administrator applies the peer group configuration on each of the BGP sessions. BGP neighbors of a single router can be divided into several groups, each group having its own BGP parameters. Actual neighbors are then bound to the appropriate group, resulting in an optimum BGP configuration.

7-36 Configuring BGP on Cisco Routers (BGP) v3.2 © 2005, Cisco Systems, Inc.

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