1. Release 5.1, Revision 0 Copyright © 2001, Juniper Networks, Inc. Advanced Juniper Networks Routing Module 7: BGP Route Reflection

2. Copyright © 2001, Juniper Networks, Inc. Objectives Describe the operation of BGP route reflection Configure a route reflector Explain the flow of routing information in a route reflection network

3. Copyright © 2001, Juniper Networks, Inc. Scaling BGP IBGP full-mesh peer requirement has an N-squared problem – Addition of a new router requires new peering with all current IBGP speakers – Current IBGP speakers must update configurations Route Reflection (RFC 2796) is one method for scaling IBGP connectivity

4. Copyright © 2001, Juniper Networks, Inc. Route Reflection Concepts Allows an IBGP speaker to re-advertise an IBGP learned route to another IBGP speaker Route Reflector (RR) only re-advertises the best route to “clients” IBGP attributes are not changed by reflection Routing Loops are prevented by new BGP attributes of Cluster-id, Cluster-list, and Originator-id

5. Copyright © 2001, Juniper Networks, Inc. Route Reflection Attributes Cluster-id represents each RR cluster in the network – RR will drop routes that have already transited the cluster – Added to the cluster-list when the RR advertises outside of the cluster Cluster-list operates like an AS_Path – RR use it for loop prevention – Routers can use it in the route selection algorithm Originator-id denotes the first router to inject a route in a RR network

6. Copyright © 2001, Juniper Networks, Inc. Route Reflection Configuration Route reflector clients are configured in a separate peer group Each peer group uses the cluster keyword – Unique 32-bit number if used as the cluster-id – Often the router-id of the RR is used Clients only peer to their route reflectors [edit protocols bgp] group int-peers { type internal; local-address 172.16.1.1; cluster 172.16.1.1; neighbor 172.16.2.2; neighbor 172.16.3.3; neighbor 172.16.4.4; } [edit protocols bgp] group int-peers { type internal; local-address 172.16.2.2; neighbor 172.16.1.1; }

7. Copyright © 2001, Juniper Networks, Inc. RR Client Full Mesh Clients may also peer with each other member of the RR cluster To stop unnecessary advertisements, configure the RR with the no-client-reflect command [edit protocols bgp] user@rr-client-1# show group int-peers { type internal; local-address 172.16.2.2; neighbor 172.16.1.1; neighbor 172.16.3.3; } [edit protocols bgp] user@rr-client-2# show group int-peers { type internal; local-address 172.16.3.3; neighbor 172.16.1.1; neighbor 172.16.2.2; } [edit protocols bgp] user@route-reflector# show group int-peers { type internal; local-address 172.16.1.1; cluster 172.16.1.1; no-client-reflect; neighbor 172.16.2.2; neighbor 172.16.3.3; }

8. Copyright © 2001, Juniper Networks, Inc. “Basic” Route Reflection Client –> RR –> clients & non-clients Non-client –> RR –> clients only

9. Copyright © 2001, Juniper Networks, Inc. Hierarchical Route Reflection Client –> RR –> clients & non-clients Non-client –> RR –> clients only

10. Copyright © 2001, Juniper Networks, Inc. Route Propagation (1 of 3) Routes are sent from a client to all peers (route reflector) 10.10.10.0/24

11. Copyright © 2001, Juniper Networks, Inc. Route Propagation (2 of 3) Route reflector sends routes to all clients in the cluster and all peers 10.10.10.0/24 10.10.10.0/24 10.10.10.0/24

12. Copyright © 2001, Juniper Networks, Inc. Route Propagation (3 of 3) Route reflector sends routes from peers to all clients in the cluster 10.10.10.0/24 10.10.10.0/24

13. Copyright © 2001, Juniper Networks, Inc. Review Questions What does a BGP route reflector do with BGP routes received from a configured RR client router? What three BGP attributes are introduced when BGP route reflection is used and what is their role?