eBGPlearned

eBGPlearned is a label used in routing to refer to routes learned through an external Border Gateway Protocol (eBGP) session from a neighboring autonomous system (AS). It distinguishes such routes from those learned via iBGP, which come from peers within the same AS. eBGP is the primary mechanism for exchanging reachability information between autonomous systems, including connections between Internet providers and large enterprises.

Characteristics of eBGP learned routes include an AS_PATH that contains the external AS, indicating external provenance; the next-hop attribute typically set to the IP address of the advertising eBGP neighbor; and a relatively low administrative distance compared with iBGP routes, which makes them preferred locally under default policies. In standard eBGP sessions, the TCP TTL is typically 1, reflecting a direct neighbor relationship.

Within an AS, eBGP learned routes are redistributed according to routing policy to internal or other external peers. Network operators use tools such as route maps, prefix-lists, and next-hop-self configurations to manage reachability, path selection, and next-hop reachability. eBGPlearned routes can be affected by policy mechanisms like AS-path prepending, MEDs, and community attributes to influence routing decisions and traffic engineering.

In practice, distinguishing eBGPlearned routes helps operators understand a route’s origin and apply appropriate policy, troubleshooting, or security checks. Some routing platforms expose a notation indicating the route’s source as external, which aids in diagnostics and policy enforcement. Overall, eBGPlearned routes form the foundation of inter-domain reachability and controlled policy propagation across network boundaries.