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SSH works fine if the user laptop and the edge device on are in the same network, either they are all on the Internet or all in a private VPN network. If the edge device is behind NAT, firewall, LTE or proxy server, and the user's laptop is not, then SSH will not work. Also in the case of the user's laptop and the device belong to the same network, if multiple users want to access the device, they all need to share the private SSH key . Sometimes that (or add multiple public keys onto the device) which sometimes is not desirable.
6) Why not just use SD-WAN
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