Cisco ASR1002 Network Positioning Guide - Page 27

Configuring the Routing Protocols Used for Network Proximity How to Configure Routing Protocols IGP Proximity Cisco NPS supports these IGP protocols: OSPF and IS-IS. The algorithm relies on the computation of a reverse shortest patch first (SPF) such that the link costs are evaluated from the PTAs towards the PSA. EGP Proximity BGP is the de-facto EGP standard and the basic algorithm for BGP proximity relies on the AS_PATH attribute. The computation is very similar to the IGP version, except that path costs are used rather than link costs. Cisco NPS does not support inter-AS topologies for proximity calculations. Proximity Source Address Route Origin To apply the correct proximity algorithm, the PXE selects the identical routing protocol from which it learned the PSA. For example, if the PXE learned the PSA from OSPF, then the proximity calculation relies on IGP proximity and automatically ranks PTAs learned from BGP lower. This works well because PTAs within the same OSPF area are preferred over PTAs in a different AS. IGP proximity and iBGP proximity are applied most frequently. How to Configure Routing Protocols Configuring OSPF for Proximity Calculations Use this task to configure the Open Shortest Path First (OSPF) routing process used for proximity calculations performed by the proximity engine. Before You Begin When using OSPF proximity calcuations, it is advised to configure the ip ospf priority command in interface configuration mode for the integrated-service interface on your router. This command helps determine the designated router (DR) / backup DR election. Router# config Router(config)# interface interface-service 0 Router(config-if)# ip ospf priority 1 SUMMARY STEPS 1. router ospf process-id 2. network ip-address wildcard-mask area area-id 3. area area-id {stub | nssa} 4. area area-id authentication {message-digest | cleartext} 5. log-adjacency-changes 6. router-id ip-address OL-25794-01 Cisco Network Positioning System Configuration Guide for the Cisco ASR 1000 Router, Release 1.0 21