CCNA Foundations: OSPF Day 3 — DR/BDR Election on a Broadcast Segment

Archive lab

Three IOS routers share a true broadcast multi-access segment through a Layer-2 switch. You will deploy OSPFv2, influence the DR/BDR election using interface priorities, and verify full adjacencies to the DR. An alpine client behind RTR-HQ-R3 must reach loopbacks on RTR-HQ-R1 and RTR-HQ-R2 via OSPF-learned routes. The lab emphasizes proper multi-access deployment hygiene (router-ids, passive default, interface selection) and realistic verification from the end host.

Learning objectives

• Configure OSPFv2 on a broadcast multi-access segment and understand DR/BDR roles
• Influence DR/BDR election using ip ospf priority on router interfaces
• Apply OSPF hygiene: stable router-ids, passive-interface default, selective no passive on transit links
• Verify adjacencies and designated router selection; validate end-to-end reachability from a host

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.