OSPF Cost & Path Selection: Deterministic Control (3 Routers)

Bundle lab · $29.99

Build a 3-router triangle with two end-to-end paths between Branch A and the Data Center. Stand up OSPF area 0, create an ECMP condition, then intentionally steer traffic using ip ospf cost. Verify from the end hosts and troubleshoot common OSPF control-plane mismatches.

Learning objectives

• Configure OSPF area 0 on addressed transit and LAN interfaces while keeping LANs passive
• Establish OSPF adjacencies and verify with neighbor and route tables
• Create ECMP and then prefer a specific path using interface costs
• Validate path selection and failover from end hosts using ping and traceroute
• Troubleshoot OSPF neighbor and route issues caused by passive-interface, area, or cost misconfiguration

Troubleshooting focus

• Verify every link's interface status and IP addressing (`show ip interface brief`) and correct any interface that is down or misaddressed.
• Confirm each device's running configuration matches the lab objective, and bring any interface, route, or service that is not in its expected state back to health.
• Trace end-to-end reachability with ping/traceroute and isolate the first hop where forwarding fails.