Acces to TCP/UDP port 53 blocked after the VPN connection is made

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monthyro
OpenVpn Newbie
Posts: 1
Joined: Wed Apr 12, 2023 6:31 am

Acces to TCP/UDP port 53 blocked after the VPN connection is made

Post by monthyro » Wed Apr 12, 2023 7:20 am

I have a strange problem in Windows 10 pro 22H2. I'm using openvpn client 3.3.7. I am not using any type of firewall on my workstation.
I connected to a VPN server from a client, I don't have access to the settings of the server, the client works in a very secured environment.
I can edit the .ovpn profile from my side.
The connection to the VPN server is made properly, I can access the hosts from the client network, also I can access any external IP address from anywhere in the world using the gateway from the client or my gateway, by my choice. But when the VPN connection is made, port 53 became unreachable. I mean any DNS server, DNS from my local network, DNS from google 8.8.8.8 and DNS from the network client. It seems that the OpenVPN client blocks the requests to port 53, doesn't matters the destination IP of DNS server.
I tried everything which I found on the Internet, succesfully changed the DNS imposed by OpenVPN server with my local DNS servers, succesfully changed the gateway for the rest of the connections excepts the client network but the 53 port became unreachable after I made the VPN connection.
I installed a local cache DNS (MaraDNS) on my computer with Windows 10, it works, but the same, it became unreachble on port 53 after I made the connection even if the MaraDNS server are accessed on 127.0.0.1:53 or localhost:53, both working without the VPN connection started.
This issue affect just my computer with Windows 10, the rest of the computers from my network can access the VPN server without port 53 became blocked. From this reason, I am not suspecting the wrong settings from the OpanVPN server belonging to the client.
If you are experiencing a similar issue and you found a solution please let me know.
Thanks,

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JosephS
OpenVPN Inc.
Posts: 54
Joined: Fri Feb 17, 2023 5:15 pm

Re: Acces to TCP/UDP port 53 blocked after the VPN connection is made

Post by JosephS » Tue Apr 18, 2023 8:05 am

Hi.
Just out of curiosity.
Is the .ovpn profile from a community server or from an openVPN Access Server?

adas444
OpenVpn Newbie
Posts: 1
Joined: Tue Apr 18, 2023 10:35 am

Re: Acces to TCP/UDP port 53 blocked after the VPN connection is made

Post by adas444 » Tue Apr 18, 2023 10:36 am

Hi,
Mine was unable to resolve. My server should be community server from pfsense

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JosephS
OpenVPN Inc.
Posts: 54
Joined: Fri Feb 17, 2023 5:15 pm

Re: Acces to TCP/UDP port 53 blocked after the VPN connection is made

Post by JosephS » Thu May 04, 2023 9:03 am

Hi adas444,

To remedy this issue so that it would work with the OpenVPN connect Client specifically, you would need to do the following:

On the PfSense admin portal you would need to go to VPN > OpenVPN > Servers > Edit Server.
After that under "Advanced Client Settings" uncheck "DNS Default Domain" and have the "DNS Server enable" option checked and provide the addresses for the dns resolvers below.

Again, this needs to be applied only if you are running the Connect client with Pfsense servers, if you are using the OpenVPN GUI community client then it should work with the default settings.
Hope it helps.

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