WEBVTT

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Three routers form a triangle, with a direct link and an alternate path.

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Use OSPF to establish IP reachability before adding segment routing.

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Enable segment routing for OSPF and configure the same global label block.

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Map each loopback prefix to its own segment identifier.

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Check the forwarding table for the destination label and direct next hop.

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Shut down the direct link so OSPF selects the path through the transit router.

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The destination label stays the same, while the outgoing interface changes.

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Use an IP ping to check loopback reachability through the alternate path.

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Shut down the remaining link and verify that the route and label are withdrawn.

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The remote loopback no longer responds while both paths are down.

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Restore the links and verify that the direct next hop and reachability return.

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Save the configuration after checking the restored path.