BGP (Border Gateway Protocol) selects the best route for a given destination using the following criteria:
1. Prefix length: BGP prefers the route with the longest prefix match.
1. Local Preference: The route with the highest local preference is preferred. This attribute is set locally within an autonomous system (AS) and is used to influence BGP route selection decisions.
1. AS Path: BGP prefers the route with the shortest AS Path. AS Path is a list of ASes that are crossed to reach the destination network.
1. Origin code: If all other attributes are the same, BGP prefers the route with the lowest origin code. The origin code is assigned by the router that advertises the route.
1. Multi-exit Discriminator (MED): If the routes originate from different ASes and have the same AS Path length, BGP prefers the route with the lowest MED. MED is a value that is set by an AS to indicate the preferred entry point into the AS.
1. IGP metric: If the routes originate from the same AS and have the same AS Path length, BGP prefers the route with the lowest IGP (Interior Gateway Protocol) metric.
1. External BGP (eBGP) over internal BGP (iBGP): If all other attributes are the same, BGP prefers the route learned from an eBGP peer over the route learned from an iBGP peer.
1. Router ID: If all other attributes are the same, BGP prefers the route advertised by the router with the lowest router ID. The router ID is a unique identifier assigned to a BGP router.
