Ali
From Cisco doc
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The Goodbye Message
The goodbye message is a feature designed to improve EIGRP network convergence. The goodbye message is broadcast when an EIGRP routing process is shutdown to inform adjacent peers about the impending topology change. This feature allows supporting EIGRP peers to synchronize and recalculate neighbor relationships more efficiently than would occur if the peers discovered the topology change after the hold timer expired.
The goodbye message is supported in Cisco IOS Release 12.3(2), 12.3(3)B, and 12.3(2)T and later releases. The following message is displayed by routers that run a supported release when a goodbye message is received:
*Apr 26 13:48:42.523: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.1.1.1
(Ethernet0/0) is down: Interface Goodbye received
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This basically means that either the eigrp process was stopped on one of the routers or the network statement for the interface that the adjacency was formed on was removed from under the eigrp config.
It should not happen on it's own.
Jon
