Billion Electric Company BiGuard 50G - Manual (Page 28)

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2.5.1 DNS Inbound Fail Over
BiGuard 50G can be configured to reply the WAN2 IP address for the DNS domain
name request should WAN1 fail.
In the above example, an FTP Server (IP_192.168.2.2) and an HTTP Server
(IP_192.168.2.3) are connected to the Internet via WAN1 (IP_200.200.200.1) on
BiGuard 50G. A remote computer is trying to access these servers via the Internet,
and makes a DNS request. The DNS request (
www.mydomain.com ) will be sent
through WAN1 (200.200.200.1) to the built-in DNS server. The DNS server will reply
200.200.200.1 because this is the only active WAN port. Should WAN1 fail, BiGuard
50G will instead reply with WAN2’s IP address (100.100.100.1), and the remote PC
will gain access to the network via WAN2. By configuring BiGuard 50G for DNS
Inbound Fail Over, incoming requests will enjoy increased reliability when accessing
your network.
Please refer to appendix H for example settings.