In the Junos OS, which attribute is used before the AS path in the BGP selection algorithm?

In the BGP selection algorithm used by the Junos OS, the attribute that is considered before the AS path is the highest local preference. Local preference is a BGP attribute that indicates the preferred path for outbound traffic from an autonomous system (AS). It is a value used to influence the BGP decision-making process, where a higher local preference value is preferred over lower values.

When BGP evaluates multiple routes to the same destination, it first looks at the local preference attribute to determine which path to use. Routes with the highest local preference are chosen before any other attributes are considered, such as AS path length. This makes local preference a crucial tool for network administrators to control routing policies within their own AS. It allows for fine-tuning of route selection based on traffic requirements or topology.

Other attributes, such as weight, lowest MED, and AS path length, are considered later in the BGP decision-making process, making local preference a primary determinant of route selection immediately after processing routes.