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3
You should disable caching of the redirection page. There are exist two options:
1) on the web server
Cache-Control: max-age=0, no-cache, no-store, must-revalidate Pragma: no-cache
2) add the ? sign to the url of the ntf_server option, it will differ from time to time
ntf_server=192.168.0.18/ntf?