BGP Configuration Guidelines > Configuring the BGP Local Preference

Internal BGP sessions use a metric called the local preference, which is carried in internal BGP update packets in the path attribute LOCAL_PREF. This metric indicates the degree of preference for an external route. The route with the highest local preference value is preferred.

The LOCAL_PREF path attribute is always advertised to internal BGP peers and to neighboring confederations. It is never advertised to external BGP peers. The default behavior is to not modify the LOCAL_PREF path attribute if it is present.

NOTE: The LOCAL_PREF path attribute applies at export time only.

By default, if a received route contains a LOCAL_PREF path attribute value, the value is not modified. If a BGP route is received without a LOCAL_PREF attribute, the route is handled locally (that is, it is stored in the routing table and advertised by BGP) as if it were received with a LOCAL_PREF value of 100. A non-BGP route that is advertised by BGP is advertised with a LOCAL_PREF value of 100 by default.

To change the local preference metric advertised in the path attribute, include the local-preference statement, specifying a value from 0 through 4,294,967,295 (2³² -1):

local-preference local-preference; 

For a list of hierarchy levels at which you can configure this statement, see the statement summary section for this statement.