Cisco CCNP / BSCI Certification: The Local Preference BGP Attribute
When studying for your BSCI exam for the CCNP, you get your first taste of BGP. One of the major differences between BGP and the other protocols you’ve studied to date is that BGP uses attributes to describe paths, and to influence the selection of one path over the other.
In this free tutorial, we’re going to take a look at the Local Preference attribute and compare it to the Cisco-proprietary BGP attribute “weight”.
The Local Preference (LOCAL_PREF) attribute is used to influence how traffic will flow from one Autonomous System (AS) to another when multiple paths exist. For example, if AS 100 has two different paths to a destination network in AS 200, the LOCAL_PREF attribute can be used to influence the path selection.
The major difference between the Weight and LOCAL_PREF attributes is that when the LOCAL_PREF attribute is changed, that change is reflected throughout the AS. The new LOCAL_PREF value will be advertised to all other routers in the AS, as compared to the Weight attribute, which is locally significant only. If you change the Weight for a...