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I have a personal VPN set up running to use TCP on port 443 which I am trying to connect to using openvpn on an iphone. Connections from a particular network are failing, yet it works fine from other networks.

I'm assuming there is some pretty strict filtering occurring, yet a generic free app connects fine. I'd like to determine what port is being used by that app so I can replicate those settings on my VPN. It's a black box with no configurable settings.

There doesn't appear to be a way to obtain this information from the phone. I poked around (via telnet) in a wifi router the phone was connected to but didn't see a way to obtain this information there either. I was thinking about trying to connect it via wifi to a laptop and using wireshark but that's starting to sound a bit complicated. Am I overlooking anything more simple?

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  • The protocol of a VPN depends on your configuration of that VPN. Your question as it's currently written cannot be answered
    – Ramhound
    Commented Mar 28, 2017 at 22:09
  • I agree, by protocol I was thinking internet protocol, not VPN protocol. At this point I'm more interested in finding out what port it's using. I can switch between TCP and UDP easily enough to test. If I know what port it's using and replicate the configuration in openvpn and it's still blocked, it's a safe bet it's using a different VPN protocol.
    – bruno617
    Commented Mar 28, 2017 at 23:47
  • VPn protocol is an Internet protocol. Are you asking what port the iOS vpn client uses? What port that is, depends on your vpn server, and which "type" your using. By type it means what type of authentication your using.
    – Ramhound
    Commented Mar 29, 2017 at 0:11

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Connections from a particular network are failing, yet it works fine from other networks.

I smell an old foe. When I was first trying to set up VPNs to my network, I stumbled upon the delightlful situation of "some locations wouldn't work" - which turned out to be "locations that used the same far too common private local addresses would not work, because they assumed that the device at (say) 192.168.1.57 they were trying to connect to was on the same local 192.168.1.0/24 that they were locally connected to, not out on the VPN.

I relocated my local addresses into the less-used parts of private address space, and it solved my problem. I can't say that it will solve yours, but it might.

Perhaps your working (app/device) is sending all traffic via the VPN?

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