Cisco ENCOR Practice Exam 2025 – All-in-One Comprehensive Guide to Mastering Enterprise Network Core Technologies!

In BGP (Border Gateway Protocol), when both paths are external, the preference is generally given to the shortest AS (Autonomous System) path. This is because BGP is designed to prevent routing loops and ensure the most efficient routing of data across the internet.

The shortest AS path attribute helps in achieving this objective by indicating the number of AS hops a route has taken. A shorter AS path is typically preferable because it suggests fewer intermediary networks, which may enhance performance due to reduced latency and lower complexity in route selection.

Choosing the longest AS path would counteract the goal of efficiency in routing. Routes with fewer AS hops will typically be preferred over routes that take a longer path. However, it is also important to note that other factors may influence this decision, but in the case of both paths being external, the shortest AS path is a standard criterion.

The notion of preferring the oldest or newest path is less relevant in this situation; BGP primarily focuses on path length in terms of AS distance for making its primary routing decisions. Therefore, the preference of the shortest AS path is aligned with BGP’s operational goals and its fundamental attributes.