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hzhang's avatar
hzhang
Copper Contributor
May 07, 2025

VPN on Windows Server 2016 not working

I followed the stand procedure to set up VPN on Windows Server 2016. Let me jump to where I am now. The event viewer has the following two entries when a client connects to the VPN server: A co...
management
networking
windows server
hzhang's avatar
hzhang
Copper Contributor
May 14, 2025

To avoid my Fios router, I tried my Android device without Wi-Fi (i.e., using only cellular connection). The Android built-in VPN client does not work and gives no information about why the connection fails.

I downloaded the app strongSwan. Its connection fails too, but it has a log: 

 

micheleariis's avatar
micheleariis
MCT
May 15, 2025

Hi, the NO\_PROPOSAL\_CHOSEN error happens because the client and server can’t agree on encryption and DH parameters for IKE. Your strongSwan settings don’t match what the server accepts.

  1. Align IKE proposals in strongSwan to match the server (e.g., aes256-sha256-modp2048)
    2. Check IPsec settings on the Windows server (Encryption, Integrity, DH Group) and make sure they match.
    3. Verify PSK or certificates are correct and identical on both sides.
    4. Test again to see if the negotiation succeeds.

If syncing the IPsec policies is too tricky, you can temporarily try SSTP (HTTPS-based VPN) to check if the rest of the setup is fine.

 

  • hzhang's avatar
    hzhang
    Copper Contributor
    May 16, 2025

    Thanks a lot for all the help. It is greatly appreciated.

    I tried but could not figure out what the server had for handshaking.

    I am giving up. I have spent too much time on this, and I don't want to waste the time of others like you.