Border Gateway Protocol - CCIE Routing and Switching Exam Certification Guide - page 445

BGP Weight Figure 9-8

Internet

AS 200

AS 100

Router C
5.1.1.1

Router B
4.1.1.1

Weight = 400 Weight = 600

Router A

AS 500

When the same destinations are advertised from both Router B and Router C in Figure 9-8,
Router A prefers the routes from Router C over Router B because the routes received from
Router C have a larger weight (600).

The configuration for Router A is shown in Example 9-13.

Example 9-13 Configuration of Weight

router bgp 500
neighbor 4.1.1.1 remote-as 100
neighbor 4.1.1.1 weight 400
neighbor 5.1.1.1 remote-as 200
neighbor 5.1.1.1 weight 600

BGP Decision Process
By default, BGP selects only a single path to reach a specific destination (unless you specify
maximum paths). Cisco's implementation of BGP uses a simple decision process. When the
path is selected, BGP puts the selected path in its routing table and propagates the path to its
neighbors.