In a hub-and-spoke topology, which IBGP setting must be enabled for ADVPN?

In a hub-and-spoke topology using the Advanced Dynamic Multipoint Virtual Private Network (ADVPN), enabling the route-reflector-client setting for Internal Border Gateway Protocol (IBGP) is crucial for proper route distribution within the network. This setting allows the hub router to manage and distribute routing information to its spoke routers efficiently.

When the hub acts as a route reflector, it can accept IBGP routes from other clients (spoke routers) and re-advertise these routes to different clients without requiring a full mesh IBGP configuration among all the spokes. This greatly simplifies the routing design and ensures that the spokes can learn about routes to other spokes or external destinations without needing direct IBGP peering between each spoke.

In the context of ADVPN, this reflects how spoke routers can dynamically establish direct connections with one another while still being able to receive and advertise routes through the hub, thus optimizing bandwidth and reducing overhead. By correctly configuring the hub to function as a route reflector, the network can achieve greater scalability and efficiency.