© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—6-1

Scaling Service Provider Networks

Configuring and Monitoring Route Reflectors

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—6-2

Outline

• Overview

• Route Reflector Backbone Migration

• Configuring Route Reflectors

• Monitoring Route Reflectors

• Summary

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—6-3

Route Reflector Backbone Migration

• Divide the AS into areas (clusters).

– Assign a cluster-ID to each area.

• On route reflector clients, retain only IBGP sessions with route reflectors in their cluster.

• On route reflectors, retain only IBGP sessions with other route reflectors and clients in their cluster.

– Configure cluster-ID on every route reflector.

– Configure clients on every route reflector.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—6-4

Configuring Route Reflectors

• Configure cluster-ID on route reflectors.

• Configure BGP neighbors as route reflector clients on the route reflectors.

• No configuration is needed on the route reflector clients.

• Make sure IBGP neighbor is removed on both ends of the IBGP session.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—6-5

bgp cluster-id cluster-idbgp cluster-id cluster-id

router(config-router)#

• Optionally assigns a cluster-ID to the route reflector (default value is router-ID)

• Required only for clusters with redundant reflectors

• Cluster-ID cannot be changed after the first client is configured

neighbor ip-address route-reflector-clientneighbor ip-address route-reflector-client

router(config-router)#

• Configures an IBGP neighbor to be a client of this reflector

Configuring Route Reflectors (Cont.)

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—6-6

Configuring Route Reflectors (Cont.)

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—6-7

Monitoring Route Reflectors

show ip bgp neighborsshow ip bgp neighbors

router#

• Displays whether a neighbor is a route reflector client

show ip bgp network [mask]show ip bgp network [mask]

router#

• Displays additional path attributes (originator-ID and cluster-list)

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—6-8

Monitoring Route Reflectors (Cont.)

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—6-9

Monitoring Route Reflectors (Cont.)

Routes received from the client as seen on the reflector

Reflected routes as seen on the client

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—6-10

Summary

• To successfully migrate an existing IBGP backbone to a backbone with route reflectors: Divide the AS into areas (clusters). On route reflector clients, retain only IBGP sessions with route reflectors in their cluster. On route reflectors, retain only IBGP sessions with other route reflectors and clients in their cluster.

• There are only two Cisco IOS commands that are used to configure BGP route reflectors: bgp cluster-id and neighbor ip-address route-reflector-client.

• The show ip bgp neighbors command will display whether a neighbor is a route reflector client, and the show ip bgp prefix command will display the originator-ID and cluster-list attributes.

© 2005 Cisco Systems, Inc. All rights reserved. BGP v3.2—6-11