Practical BGP

BGP Custom Decision Process

While the BGP best path algorithm described in Chapter 1 can be very complex, it doesn't address every possible route choice a network designer might want. One example is illustrated in Figure 7.1.

Figure 7.1. Custom metrics.

Autonomous system 65500's system administrator has a simple plan he'd like to implement for traffic being forwarded out of his network:

• Route through the shortest path, in terms of AS Path, to reach the destination.

• If both paths are equal length, route out the closest exit point.

• If both exit points are equally distant, use the cheaper path (administratively defined, based on the cost of using the ...