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[ScreenOS] Proxy DNS feature fails when loopback interface is used as outgoing-interface



Article ID: KB10419 KB Last Updated: 11 Aug 2010Version: 3.0
If loopback IP address is used as outgoing-interface in Proxy DNS configuration, a specific route to the DNS server needs to be configured on the loopback interface.
In a route-based VPN scenario, IP address of the loopback interface might be used as the outgoing-interface for Proxy DNS feature as it is the only routable IP address inside the VPN tunnel, but simply specifying loopback address of outgoing interface in Proxy DNS setting is not sufficient.
In order for   set dns server-select domain DOMAIN.NAME outgoing-interface loopback.1 primary-server IP_address_of_internal_name   to function properly, it needs to have route of the IP_address_of_internal_name server on loopback interface.

set interface loopback.1 ip
set dns host dns1 src-interface loopback.1
set dns server-select domain outgoing-interface loopback.1 primary-server

set route gateway

Please note that Proxy DNS feature will not work when used with policy based VPN KB3680

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