OpenVPN从2.5.6升级到2.6.12后移除key-method 2选项，iOS设备无法连接的替代方案咨询

Hey there, let's break down your problem and figure out how to get those iOS devices connected again!

First off, you're right that key-method 2 was removed starting in OpenVPN 2.5—this old key negotiation method is no longer supported, and while Android clients might be more forgiving or updated to handle the modern defaults, iOS's OpenVPN client often needs a bit more explicit configuration to make the switch smoothly.

Looking at your current server config, here are the key adjustments you can make to get iOS devices back online:

1. Update TLS Authentication to Use tls-crypt (Recommended) #

The tls-auth option you're using is still valid, but pairing it with modern key negotiation (replacing the old key-method 2) works better with iOS when using tls-crypt instead. This not only handles the key exchange securely but is fully supported by recent iOS OpenVPN clients.

Here's how to adjust your config:

• Replace the existing tls-auth line with:

  tls-crypt "C:\\ProgramData\\VPN\\TA.key"
  

• You'll also need to update your iOS client profiles to use tls-crypt instead of tls-auth—make sure the TA.key is included in the profile and the setting is switched over.

2. Explicitly Set Minimum TLS Version #

iOS clients can be strict about TLS versions, so adding a line to enforce a modern TLS version ensures compatibility:

tls-version-min 1.2

Add this line somewhere in your server.conf (after the TLS-related options like auth or ca makes sense).

3. Verify iOS Client Version #

Make sure the iOS devices are running the latest version of the official OpenVPN Connect app. Older versions might not support the modern key negotiation methods that OpenVPN 2.6 uses by default.

4. Check for Other Compatibility Issues #

• Double-check that your dh parameter is using a supported size—dh2048.pem is fine, but if you ever switch to a larger one (like 4096), some older iOS devices might struggle.
• Ensure the push "redirect-gateway" line in your config is complete (it looks cut off in your snippet)—a malformed push command could cause connection failures on iOS specifically.

Once you make these changes, restart your OpenVPN server and test the iOS connection again. Most of the time, switching to tls-crypt and setting the TLS version minimum fixes the iOS compatibility issue after removing key-method 2.

备注：内容来源于stack exchange，提问作者Priyanka Chauhan