If these component routes are aggregated or configured as a multipath, the cost value 200 is advertised,
because it has the highest cost.
If one or more component routes do not carry the cost community attribute or the component routes are
configured with different IDs, then the default value (2147483647) is advertised for the aggregate or
multipath route. For example, the following three component routes are configured with the cost
community attribute using an inbound route policy. However, the component routes are configured with
two different IDs.
• 10.0.0.1
• POI=IGP
• cost community ID=1
• cost number=100
• 172.16.0.1
• POI=IGP
• cost community ID=2
• cost number=100
• 192.168.0.1
• POI=IGP
• cost community ID=1
• cost number=200
The single advertised path includes the aggregate cost communities as follows:
{POI=IGP, ID=1, Cost=2147483647} {POI-IGP, ID=2, Cost=2147483647}
Influencing Route Preference in a Multiexit IGP Network
This figure shows an IGP network with two autonomous system boundary routers (ASBRs) on the edge. Each
ASBR has an equal cost path to network 10.8/16.
Figure 1: Multiexit Point IGP Network
Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 6.4.x
24
Implementing BGP
Influencing Route Preference in a Multiexit IGP Network