Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 199

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) 199