Practical BGP

Policy Instruments

Policy instruments are where the policies a network administrator would like to enforce are actually encoded. There are various mechanisms used to specify these policies, including access lists, prefix lists, community lists, AS path lists, and route maps; we could consider these policy primitives, since they are the basic building blocks through which a policy may be imposed on a BGP route and the various path attributes associated with it.

Table 6.1 provides a reference for CIDR and IP addressing; a fundamental understanding of this table is integral to successful policy instrumentation. While this table provides the values associated with traditional classful Internet address space, it's important to remember these classful ...