RouteLeaks

RouteLeaks refer to the unintended propagation of routing information within Internet routing, most commonly in the Border Gateway Protocol (BGP). A route leak occurs when routes learned from one BGP neighbor or policy set are advertised to another neighbor in a way that violates the intended routing policy or trust boundaries. This can cause prefixes to be advertised beyond their intended scope or with altered path attributes, potentially leading to suboptimal routing, instability, or traffic being directed through unintended networks.

Causes of route leaks often include misconfigured route filters or prefix lists, incorrect use of BGP communities, improper redistribution between different routing domains, or the use of route reflectors and confederations that do not preserve export policies. Leaks can arise from human error, automated policy changes, or interoperability gaps between networks with different policy interpretations. They can occur within an organization’s own network as well as between operators that peer with each other.

Impact ranges from degraded performance and increased latency to temporary loss of reachability or exposure of traffic to additional networks. While route leaks share some symptoms with route hijacks, they are typically policy violations rather than deliberate attempts to take control of routes; however, their effects can be similar, including traffic misrouting and instability.

Mitigation and detection efforts emphasize strict policy design and enforcement. Techniques include thorough prefix filtering, AS-path filtering, careful use of BGP communities and route targets, and limiting redistribution between routing domains. Adoption of RPKI for origin validation, robust monitoring with route collectors and looking-glass tools, and participation in routing security initiatives (such as MANRS) help reduce the risk and impact of route leaks.