WEBVTT

1
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Three Cisco routers form the lab, with the middle router carrying the underlay traffic.

2
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Verify that the far tunnel endpoint is reachable through the physical network.

3
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Configure a GRE tunnel on each edge router using its loopback as the source.

4
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Check that the tunnel is up and that the overlay route uses it.

5
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Ping the far tunnel address to verify that traffic crosses the overlay.

6
00:01:23.850 --> 00:01:31.850
Shut down the far side of the transit router to break the underlay path.

7
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Both the endpoint and the overlay become unreachable.

8
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Restore the transit link and verify that the endpoint and overlay are reachable again.