Below is the BGP path selection process which I copied from Cisco’s site :

BGP Path Selection

BGP could possibly receive multiple advertisements for the same route from multiple sources. BGP selects only one path as the best path. When the path is selected, BGP puts the selected path in the IP routing table and propagates the path to its neighbors. BGP uses the following criteria, in the order presented, to select a path for a destination:

•If the path specifies a next hop that is inaccessible, drop the update.

•Prefer the path with the largest weight.

•If the weights are the same, prefer the path with the largest local preference.

•If the local preferences are the same, prefer the path that was originated by BGP running on this router.

•If no route was originated, prefer the route that has the shortest AS_path.

•If all paths have the same AS_path length, prefer the path with the lowest origin type (where IGP is lower than EGP, and EGP is lower than incomplete).

•If the origin codes are the same, prefer the path with the lowest MED attribute.

•If the paths have the same MED, prefer the external path over the internal path.

•If the paths are still the same, prefer the path through the closest IGP neighbor.

•Prefer the path with the lowest IP address, as specified by the BGP router ID.