routereflector

A route reflector is a BGP router that reduces the need for a full iBGP mesh within an Autonomous System by acting as a central distribution point for routes learned via iBGP. By designating route reflector clients, the reflector forwards routes between them rather than requiring every peer to be peered with every other peer.

How it works: In networks with many iBGP speakers, full mesh can be expensive. A route reflector collects routes from its clients and from other reflectors, and reflects them to other clients. To prevent loops, reflected routes carry a cluster-list attribute that includes the reflector’s cluster ID; a route with a matching ID is not reflected again.

Next-hop handling: When a route is advertised to iBGP clients by a route reflector, the next-hop attribute is typically preserved (not rewritten) for routes learned via iBGP; routes learned from eBGP keep the eBGP next-hop, which must remain reachable by the clients.

Topology and management: Route reflectors are commonly deployed in hub-and-spoke topologies or in a hierarchical arrangement where multiple reflectors serve as clients for each other. Redundancy is typically achieved with multiple reflectors and diverse client assignments.

Advantages and limitations: Route reflectors reduce scaling costs and simplify configuration in large networks, but introduce potential single points of failure, possible suboptimal routing, and risk of misconfiguration leading to route leaks. They require careful planning, monitoring, and security controls.

Background: The concept was formalized in the BGP Route Reflection RFC (RFC 4456). In practice, route reflectors are widely used in large service provider networks and data centers to enable scalable iBGP deployment.