Name: See OSPF routing and its topology overlay
Uploaded: 2026-10-05
Duration: PT242.9S

See OSPF routing and its topology overlay

Configure OSPFv2 area 0 on two prepared routers, use unique router IDs and network statements for the connected and loopback interfaces, and save the configuration. Verify the neighbor, learned route and real traffic, then use the OSPF display filter to show or hide orange adjacency indicators. Disconnect and restore the same cable to diagnose and confirm recovery. The animated indicators represent protocol activity; they are not captured packets. This episode covers a single area-0 pair. Cost, alternate paths, authentication and OSPFv3 are covered separately.

English narration and on-screen explanations. Read the narration transcript.

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Start with a connected pair
R1 and R2 are connected on Gi0/0. Each router also has a loopback address.
The directly connected address replies, but the remote loopback has no route yet.
Configure OSPF on both routers
R1 uses process 1 and a unique router ID. Both routers join area 0.
The network statements enable OSPF on matching interfaces. Save the configuration.
R2 uses process 1 and a unique router ID. Both routers join area 0.
The network statements enable OSPF on matching interfaces. Save the configuration.
Verify the neighbor, route and traffic
The neighbor is FULL. The O entry is the learned route to R2’s loopback.
The remote loopback now replies with 100 percent success.
Show and hide OSPF indicators
The orange OSPF indicators show the active adjacency on this link.
This checkbox changes the display. It does not disable OSPF on the routers.
Recognize a failed link
Confirm the exact connection before disconnecting it.
The physical interface is down, the neighbor is gone, and the remote route is absent.
Restore the connection and confirm
Reconnect R1 and R2 on the same Gi0/0 ports.
Verify the recovered neighbor, learned route, and successful traffic.
The OSPF indicators return when the adjacency is healthy again.