Refer to the exhibit. A company recently deployed a new network using OSPF in the core to share routes. The network administrator selected OSPF as the routing protocol because of its ability to maintain a route database. When the new network was started up, all routers booted normally, but the link between routers R1 and R2 failed to come up. The two routers are located in the same rack at the data center. Which task should an engineer perform to correct the problem?