- A network where messages are being delivered from the ingress router, across a neighbor router to a third router where the destination is attached.
- The neighbor router is shut down.
- There is a valid alternative path to the destination.
- A message delivery arrives immediately after the neighbor router is lost (before the route engine can compute the new path).
In the above scenario, the delivery may wind up on the ingress link's "undelivered" list and stay there indefinitely, even after the network has been completely restored.