There was a SIP phone called the Zultys ZIP4x5 that had VPN built in and could do something like you described, but I don't think they are made any more. Also, it wasn't exactly 'automatic' you would have to preconfigure the VPN settings before deploying. I think you will need to put something like a 851 at the remote site and have the VPN configured before plugging the phone in.
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Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.