Red Hat 8 vpn client can't connect to OpenVPN server on router ac5300

Question

I am using Red Hat 8 (rhel8), my home router is Asus AC5300 running OpenVPN server. But my rhel8 VPN in Network Manager can't not connect to my OpenVPN Server.

Here is the error message I got:

[root@my-machine ~]# journalctl -f nm-openvpn[30404]: TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled. This can be caused by mismatched tls-version-min and tls-version-max options on client and server. If your OpenVPN client is between v2.3.6 and v2.3.2 try adding tls-version-min 1.0 to the client configuration to use TLS 1.0+ instead of TLS 1.0 only

[root@my-machine ~]# openvpn --version
OpenVPN 2.4.7 x86_64-redhat-linux-gnu

I've tried by adding tls-version-min 1.0 to my .ovpn file but still not working.

Note: In Linux Ubuntu it is working just fine, BUT not Red Hat 8

Answer 1

seems you have a problem with TLS ... take a look to this checks , maybe have to take a look SSL certificates:

Check for Certificate Name Mismatch

In this particular instance, the customer migrating to Kinsta had a certificate name mismatch which was throwing up the ERR_SSL_VERSION_OR_CIPHER_MISMATCH error. As you can see from the SSL Labs test below, this is pretty quick and easy to diagnose. As SSL Labs states, a mismatch can be a number of things such as:

The site does not use SSL, but shares an IP address with some other site that does.
The site no longer exists, yet the domain still points to the old IP address, where some other site is now hosted.
The site uses a content delivery network (CDN) that doesn’t support SSL.
The domain name alias is for a website whose name is different, but the alias was not included in the certificate.

Certificate name mismatch

Another easy way to check the current domain name issue on the certificate is to open up Chrome DevTools on the site. Right-click anywhere on the website and click on “Inspect.” Then click on the security tab and click on “View certificate.” The issued domain will show in the certificate information. If this doesn't match the current site you're on, this is a problem. Check issued domain on SSL certificate

Check issued domain on SSL certificate

Remember though, there are wildcard certificates and other variations, but for a typical site, it should match exactly. However, in our case, the ERR_SSL_VERSION_OR_CIPHER_MISMATCH error actually prevented us from being able to check it in Chrome DevTools. That is where a tool like SSL Labs can come in handy. Check for Old TLS version

Another possible reason is that the TLS version running on the web server is old. Ideally, it should be running at least TLS 1.2 (better yet, TLS 1.3). If you are a Kinsta customer you never have to worry about this as we always upgrade our servers to the latest and greatest supported versions. Kinsta supports TLS 1.3 on all of our servers and our Kinsta CDN. Cloudflare also enables TLS 1.3 by default.

(Suggested reading: if you're using legacy TLS versions, you might want to fix ERR_SSL_OBSOLETE_VERSION Notifications in Chrome).

This is something the SSL Labs tool can also help with. Under configuration, it will show you the current version of TLS running on the server with that certificate. If it is old, reach out to your host and ask them to update their TLS version. TLS 1.3 server support

TLS 1.3 server support Check RC4 Cipher Suite

Another reason according to Google's documentation for ERR_SSL_VERSION_OR_CIPHER_MISMATCH is that the RC4 cipher suite was removed in Chrome version 48. This is not very common, but it could happen in say larger enterprise deployments that require RC4. Why? Because everything usually takes longer to upgrade and update in bigger and more complex configurations.

Security researchers, Google, and Microsoft recommend that RC4 be disabled. So you should make sure the server configuration is enabled with a different cipher suite. You can view the current cipher suite in the SSL Labs tool (as seen below). Cipher suite

Cipher suite Try Clearing the SSL State On Your Computer

Another thing to try is clearing the SSL state in Chrome. Just like clearing your browser's cache this can sometimes help if things get out of sync. To clear the SSL state in Chrome on Windows, follow these steps:

Click the Google Chrome – Settings icon (Settings) icon, and then click Settings.
Click Show advanced settings.
Under Network, click Change proxy settings. The Internet Properties dialog box appears.
Click the Content tab.
Click “Clear SSL state”, and then click OK.
Restart Chrome.

Clear SSL state in Chrome on Windows

Clear SSL state in Chrome on Windows

If you are on a Mac, see these instructions on how to delete an SSL certificate. Use a New Operating System

Older operating systems fall out of date with newer technologies such as TLS 1.3 and the latest cipher suites as browsers stop supporting them. Specific components in the latest SSL certs will simply stop working. Google Chrome, in fact, pulled the plug on Windows XP back in 2015. We always recommend upgrading to newer operating systems if possible, such as Windows 10 or the latest version of Mac OS X. Temporary Disable Antivirus

The last thing we recommend trying if you are still seeing the ERR_SSL_VERSION_OR_CIPHER_MISMATCH error is to ensure you don't have an antivirus program running. Or try temporarily disabling it. Some antivirus programs create a layer between your browser and the web with their own certificates. This can sometimes cause issues.