Problem with "device" HTTP" - PRobe - Help me please

Hello all

I add “device” with address (DNS name) http://www.test.it (local address) with Type: Web Service and “services” HTTP (standard probe)

The Dude, resolve ip (10.20.20.4) and test services HTTP response it’s all ok.
But, i think that “the dude http” have problem, because i think this program TEST HTTP/TCP IP on port 80, but general Web Service, that is it does not control " address intranet" (http://www.test.it)
Therefore if i set wrong DNS NAME in “device” (For example http://www.testasdasdadas.it) the TEST HTTP/TCP IP on port 80 response it’s all ok.

Test HTTP, Response FAIL only when GENERAL WEB SERVICE is OFFLINE

How I can make in order to resolve this problem?

Sorry for my english.

thx for now

by gabar