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    OpenVPN and MTU questions? Vs vpn packet processing settings

    OpenVPN
    mtu openvpn mss vpn tunnel
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    • JonathanLeeJ
      JonathanLee
      last edited by

      Hello fellow Netgate community members can you please help?

      I have been trying to figure this out for a while.

      So my ping tests show I have 1472MTU take that add 28 and my wan is 1500 without the vpn. What should the MTU be set to on advanced settings for OpenVPN? I originally set my mss clamping on advanced settings/firewall nat/ vpn packet processing maximum mss to 1300 of the firewall and this gave me massive speed increases.

      What should I use under openVPN side? Or should I delete the max mss 1300 and set something else on the vpn ?

      Advanced settings options:
      tun-mtu?? mssfix?? tun-mtu-extra?? fragment??

      Why does setting the

      Make sure to upvote

      1 Reply Last reply Reply Quote 0
      • N
        nattygreg
        last edited by nattygreg

        My current setup that works well with openVPN for me is

        tls-client;
        remote-random;
        tun-mtu 1500;
        tun-mtu-extra 32;
        mssfix 1450;
        persist-key;
        persist-tun;
        reneg-sec 0;
        remote-cert-tls server;
        auth-retry nointeract;
        auth-nocache;

        I hope this helps, I had to tweak those settings until I stop getting gate way errors, because VPN providers for the most part will not give you these settings. This is in the customs section on openvpn.

        JonathanLeeJ 1 Reply Last reply Reply Quote 1
        • JonathanLeeJ
          JonathanLee @nattygreg
          last edited by

          @nattygreg Thanks I have attempted many trail and error tests, another one that gave me speed boosts was changing these settings.

          Screenshot 2025-03-03 at 21.50.05.png

          Make sure to upvote

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