A network engineer is configuring RIP as the routing protocol between multiple PEs and CEs.

To avoid advertising the same routes back to their sources when using RIP as the routing protocol between multiple PEs and CEs, the network engineer should define VRFs (Virtual Routing and Forwarding) on each device. VRFs allow for traffic separation by creating separate routing tables for different VPNs or customers. By using VRFs, each CE-PE link can be associated with a specific VRF, ensuring that routes are not inadvertently advertised back to their sources. Other options (A, B, and D) are not directly related to this specific requirement. References: Implementing and Operating Cisco Service Provider Network Core Technologies source documents or study guide.