In IPv4 networks, Dead Gateway Detection prevents a router from being marked offline under certain circumstances. Prior to the implementation of this feature, if PING commands were disabled on a router and a single destination became unavailable, the router was marked offline and was not used, even though it was in use by other dialogs to other hosts.
The Dead Gateway Detection feature prevents this from happening as follows. The TCPIPSUPPORT library sends a PING request, checks RIP input, and issues an ARP request to determine if a gateway is reachable
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If an ARP reply is received and a PING reply is not received, the gateway is not marked as offline and Dead Gateway processing does not select a new gateway.
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If neither an ARP reply nor a PING reply is received, the gateway is marked as offline and a new gateway is selected, if available.
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If RIP messages are received from a gateway that is suspected of being offline, the status of the router remains active.
You can use the DeadGatewayTO option to configure the time-out duration for Dead Gateway Detection. For more information, see the Networking Commands and Inquiries Help.
