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
Cisco Network Positioning System Configuration Guide for the Cisco ASR 1000 Router, Release 1.0
OL-25794-01 21
Configuring the Routing Protocols Used for Network Proximity
How to Configure Routing Protocols
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