Users Guide

Weight
The weight attribute is local to the router and is not advertised to neighboring routers.
If the router learns about more than one route to the same destination, the route with the highest weight is preferred. The
route with the highest weight is installed in the IP routing table.
Local Preference
Local preference (LOCAL_PREF) represents the degree of preference within the entire AS. The higher the number, the greater
the preference for the route.
Local preference (LOCAL_PREF) is one of the criteria used to determine the best path, so keep in mind that other criteria may
impact selection, as shown in the illustration in Best Path Selection Criteria. For this example, assume that thelocal preference
(LOCAL_PREF) is the only attribute applied. In the following illustration, AS100 has two possible paths to AS 200. Although the
path through Router A is shorter (one hop instead of two), the LOCAL_PREF settings have the preferred path go through Router
B and AS300. This is advertised to all routers within AS100, causing all BGP speakers to prefer the path through Router B.
Figure 22. BGP Local Preference
Multi-Exit Discriminators (MEDs)
If two ASs connect in more than one place, a multi-exit discriminator (MED) can be used to assign a preference to a preferred
path.
MED is one of the criteria used to determine the best path, so keep in mind that other criteria may impact selection, as shown
in the illustration in Best Path Selection Criteria.
Border Gateway Protocol IPv4 (BGPv4) 165