200-301 Question #1756: Real Exam Question with Answer & Explanation

Question

Lab Simulation 64 Please use the "Tasks" and "Topology" tabs to complete this lablet. Topology Tasks Refer to the topology. All physical cabling is in place. Routers R2 and R3 are inaccessible. Configure OSPF routing for the network and ensure R1 has joined Area 0 as the Designated Router (DR). Task 1 Configure OSPF on R1 and ensure R2 and R3 become neighbors. - use process ID 111 - use Lo0 IP as the router ID - advertise connected networks using an inverted subnet mask to match the exact prefixes used Task 2 Ensure R1 always becomes the DR for Area 0 on all links. Answer: Task 1 - Enable OSPF (PID 111), use Lo0 as router ID, advertise exact prefixes R1# conf t ! interface Loopback0 ip address 10.0.1.1 255.255.255.255 ! (example Lo0 IP - use the one from the lab) ! router ospf 111 router-id 10.0.1.1 ! use the Loopback0 IP network 10.0.112.0 0.0.0.3 area 0 ! 10.0.112.0/30 link to R2 network 10.0.113.0 0.0.0.7 area 0 ! 10.0.113.0/29 link to R3 network 10.0.1.1 0.0.0.0 area 0 ! Loopback0 /32 OSPF process 111 is created, the router-id is set to the Loopback0 IP, and each connected network is advertised with a wildcard mask that matches its exact prefix (/30 → 0.0.0.3, /29 → 0.0.0.7, /32 → 0.0.0.0). This lets R2 and R3 form OSPF neighbor adjacencies with R1 in Area 0. Task 2 - Make R1 always the DR on all Area 0 links interface e0/0 ip ospf priority 255 ! interface e0/1 ip ospf priority 255 On multiaccess OSPF networks, the router with the highest interface priority becomes the DR. Setting the OSPF priority to 255 on R1's Area 0 interfaces ensures R1 always wins the DR election on those links.

Options

• taskConfigure OSPF routing on R1 to ensure R2 and R3 become neighbors and R1 is the Designated Router (DR) for Area 0 on all links. This configuration must use process ID 111, R1's Loopback0 IP as the router ID, and advertise connected networks using inverted subnet masks.
• prerequisitesAll physical cabling is in place. Routers R2 and R3 are inaccessible.