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| 9.6 |  | BGP Attributes |
| 9.6.1 |  | Controlling BGP routing with attributes |

Traffic inside and outside an AS always flows according to the road map laid out by routes. If the routes are altered, the traffic behavior will be affected. The following are among the questions that organizations and service providers ask about controlling routes:

- How can the private networks be prevented from being advertised?
- How can routing updates that come from a particular neighbor be filtered?
- How can it be specified to use this link or this provider rather than another one?

Through the use of attributes, BGP provides the answer to all these questions and more.

A BGP speaker can receive updates from multiple autonomous systems that describe different paths to the same destination. It must then choose the single best path for reaching that destination. Once chosen, BGP propagates the best path to its neighbors. The decision is based on the value of attributes, such as Next Hop or Local Preference, that the update contains and other configurable BGP factors. The following sections provide an overview of these key attributes that BGP uses in the decision making process:

- Next Hop
- AS_Path
- Atomic Aggregate
- Aggregator
- Local Preference
- Weight
- Multiple Exit Discriminator (MED)
- Origin

| Web Links Configuring BGP http://www.cisco.com/univercd/cc/td/doc/product/ software/ios122/122cgcr/fipr_c/ipcprt2/1cfbgp.htm