Practical BGP

Local Preference

Local preference is the “big stick” of metrics within an autonomous system; since it's at the beginning of the decision process (only subsequent to the local non-BGP weight attribute), setting the local preference to a high value typically causes a route to win the selection process regardless of the other attribute values (e.g., MED or AS Path) carried with the route. As such, local preference plays a key role in most well-designed routing policies.

The default local preference value for most implementations is 100. It's extremely important that this value be consistent on all BGP speakers within your autonomous system. The default local preference value can be altered by configuring bgp default local-preference <value> within ...