DNS Query - reply from unexpected source

OK, I think you should enable the external VLANs on the first Virtual Server and apply a packet filter or iRule to restrict inbound traffic to the 100.x addresses, and the necessary source ports, remove the 100.x Virtual Server. If you don't like the sound of that I'd suggest you create a Virtual Server for each outbound service instead and again, enable on the external VLANs. Make sure in the FastL4 profile you use that Loose Initiation and Loose Close are disabled.

 

 

Currently, the second more specific VS is handling the return traffic rather than the first VS the outbound connections pass through and this is the cause of your issue.