To prevent routing loops for routes advertised between data-center sites over the SD-WAN fabric, which attribute must be configured on the routers?

Configuring the same OMP overlay-AS on WAN Edge routers across all data centers is crucial for preventing routing loops when advertising routes between sites over the SD-WAN fabric. OMP (Overlay Management Protocol) uses the overlay-AS path as a loop prevention mechanism, similar to BGP's AS path. If a router receives a route with its own overlay-AS in the path, it discards the route, preventing loops. Static routing (first option) is not scalable for large SD-WAN deployments and doesn't inherently provide loop prevention across multiple sites in the same way OMP does. Using the same BGP AS between CE and PE routers (second option) or between WAN Edge and CE routers (fourth option) is relevant for the underlay routing domain but doesn't directly address loop prevention within the SD-WAN overlay fabric managed by OMP.