What does MED stand for in networking terms?

In networking, MED stands for Multi-Exit Discriminator. It is an attribute used in BGP (Border Gateway Protocol) to influence the selection of routes from neighboring autonomous systems (ASes). When multiple paths to a destination exist, the MED value helps determine which path should be preferred by neighboring ASes.

When a BGP speaker advertises routes to external neighbors, it may include the MED value to indicate a preference for one exit point over another. A lower MED value is typically considered more desirable, and this influences inbound traffic decisions. Essentially, MED serves as a way for an AS to signal to other networks which of its links should be used for returning traffic towards it.

This capability is particularly important in scenarios where an organization has multiple connections to the Internet or different service providers and aims to manage traffic effectively based on its network topology. It ensures that the routing behavior aligns with the organization's operational policies, ultimately optimizing routing choices based on performance, cost, or other criteria.