Advanced IP Network Design (CCIE Professional Development)

Mechanics of a Path Vector Protocol

BGP is unique among all the currently used routing protocols because it relies on information about the vector (direction) to a destination and the path to a destination to prevent routing loops. All other commonly used routing protocols, such as OSPF, IS-IS, and EIGRP, rely on metrics or costs combined with some level of topology information to prevent routing loops.

Look at Figure D-1 for an example of the operation of a path vector protocol.

Suppose that Router A originates a route to 10.1.1.0/24 toward Router B. In the information on how to reach this destination, Router A notes that it is the first router in the path. Router B receives this route, adds itself to the path, and advertises the destination ...