ROUTING DOMAIN CONFEDERATIONS

As large enterprises, such as ISPs, become even larger, one autonomous system can become unwieldy. The IBGP configurations can become quite complex, and a router may have to support many internal BGP sessions. One method to deal with this problem is to “divide and conquer,” break the AS down into smaller parts.

An autonomous system can be divided into multiple autonomous systems, and grouped into a single confederation. To the outside, this partitioning is transparent, and the divided ASs appear as one autonomous system. Figure 7-9 shows the idea of the routing domain configuration.

Figure 7-9. A Routing Domain Confederation

Each of the autonomous systems is fully meshed within itself and has connections to the ...

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