Name the three ways BGP policies can be implemented.

• A. For all networks owned by an AS
• B. For a certain classless interdomain routing block of network numbers
• C. For individual networks
• D. For the long sentence

Answer: (D)

BGP policy can be applied at different levels of scope to give you the right balance of broad control and fine-grained precision. The three practical ways are: a policy that applies to all networks owned by a given AS, a policy that targets a classless interdomain routing block (a CIDR group of prefixes), and a policy that applies to individual prefixes. Applying policy to all networks from an AS lets you set rules that affect every route the AS speaks or accepts. Targeting a CIDR block lets you manage a group of prefixes with the same rules, which is useful for uniform treatment of related networks. Policy for individual prefixes provides the most granular control, enabling exceptions or special handling for specific routes. The idea described as a “long sentence” isn’t a valid method for implementing BGP policy, whereas these three levels are the common, meaningful approaches.