IP restriction is a security feature of proxy connections that makes sure that the computer using the connection has the same public IP as the one which originated the connection. If you wish to share a proxy connection with someone else, you have to disable IP restriction.
IP restriction does not work on http(s) reverse proxy connections. These are public. Security is added by use of the random subdomain, e.g. https://nf87yxfZ62cwm9m.p27.rt3.io/
Sometimes you may encounter situations where connections won't work unless IP restriction is disabled.
Proxy connections from the remote.it web portal
As noted on the connection dialog by the "make public" checkbox, "Mobile providers may use multiple source IP addresses. You may need to disable IP restrictions to connect to your devices from these platforms. NOTE: IP restriction will remain off for the duration of the connection."
Any situation where the given link is used to establish a connection to a device will "latch" the connection to that initial public IP address. So for example, if you initiate a proxy connection from the hotel, and later relocate to the office, you will have to make a new connection as the original one is latched to the hotel's public IP address.
Proxy connections from the REST API
If you are using the /device/connect REST API endpoint, documented at https://docs.remote.it/api-reference/devices/connect , you need to use your client side external IP address for the "hostip" parameter to enable IP restriction. To disable IP restriction, set "hostip" to "0.0.0.0" when making the /device/connect API call.