OpenVPN warning: No server certificate verification method has been enabled

CrimpOn
Guru - Experienced User
Dec 10, 2023
Things may have changed since those messages in 2019. Perhaps it would be helpful to start a new discussion.

It would be useful to know:

What specific device is being used to test the OpenVPN feature. (Android phone, iPhone, tablet, laptop, etc.)

How the test is being conducted. My typical procedure is to

Disconnect my Android phone from the Orbi LAN

Then, run the OpenVPN app on the phone.

Having verified that this works

Open a WiFi Hot Spot on the phone.

Disconnect a tablet or laptop from the Orbi LAN.

Connect this device to the phone Hot Spot

Verify that it gets internet.

Run the OpenVPN app on this device.

Verify that it connects to the Orbi LAN by using a web browser to open the Orbi web administration and to access other devices on the Orbi LAN

How nmap is being run to detect open ports. The Orbi WAN port cannot be observed from the LAN side, and ports opened for OpenVPN host do not appear on the Port Forwarding page. (Technically, they remain in the router, and are thus not 'forwarded'.)
Just a tiny note: Unlike TCP, UDP ports do not respond to connection attempts. The default port settings for OpenVPN are UDP port 12973 for tun connections and port 12974 for tap connections, so an nmap scan from the WAN side is not likely to reveal that port UDP is the default because it is so much more efficient than TCP. If a test is important, then the TCP option should be chosen and new parameter files downloaded.
- brian1918
  Aspirant
  Dec 10, 2023
  Thanks for your response.
  My device is a Windows 11 laptop and Windows 10 tablet for more testing.
  My test matches what you describe. Setting up while on the Orbi lan, then trying to connect from an android hotspot (internet works from the phone). The nmap port scan was from the Orbi LAN.
  nmap -sS <Orbi gw>
  Host is up (0.0010s latency).
  Not shown: 996 closed tcp ports (reset)
  PORT STATE SERVICE
  21/tcp filtered ftp
  53/tcp open domain
  80/tcp open http
  443/tcp open https
  
  nmap -sU <Orbi gw>
  Host is up (0.00044s latency).
  Not shown: 991 closed udp ports (port-unreach)
  PORT STATE SERVICE
  22/udp open|filtered ssh
  23/udp open|filtered telnet
  53/udp open domain
  67/udp open|filtered dhcps
  69/udp open|filtered tftp
  161/udp open|filtered snmp
  162/udp open|filtered snmptrap
  1900/udp open|filtered upnp
  5351/udp open nat-pmp
  
  Interestingly - earlier today, On the Orbi LAN, without making any changes, the VPN connected, the network vpn adapter was configured with an IP. So, I disconnected from the LAN, then connected to the cell phone hot spot... The VPN never connected, connecting back to the LAN didn't connect again either. weird.
  
  Been through the setup instructions maticulously, but nogo. There must be some additional requirements/instructions to clear up an out of the box VPN configuration.
  
  Appreciate all your assistance. Thanks.
  - CrimpOn
    Guru - Experienced User
    Dec 11, 2023
    Thanks for the details.
    
    nmap cannot detect OpenVPN from the LAN side. useful tool much of the time, but not for this.
    
    the Android phone providing the Hot Spot was disconnected from the Orbi LAN WiFi ... correct?

Forum Discussion

OpenVPN warning: No server certificate verification method has been enabled