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    OpenVPN and DCO

    Scheduled Pinned Locked Moved OpenVPN
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    • F
      frodet
      last edited by

      When activating DCO Offloading on my OpenVPN server i get these warnings in the client log:

      Wed Aug 03 23:34:55 2022 WARNING: 'link-mtu' is used inconsistently, local='link-mtu 1569', remote='link-mtu 1549'
      Wed Aug 03 23:34:55 2022 WARNING: 'cipher' is used inconsistently, local='cipher AES-256-CBC', remote='cipher AES-256-GCM'
      Wed Aug 03 23:34:55 2022 WARNING: 'auth' is used inconsistently, local='auth SHA256', remote='auth [null-digest]'

      I have a Netgate SG-1100. The connection works like intended. VPN speed is at least five fold with DCO Offload enabled and SafeXcel activated.

      Should I worry about these warnings?

      F 1 Reply Last reply Reply Quote 0
      • F
        frodet @frodet
        last edited by

        So, no one has any idea about this?

        JeGrJ 1 Reply Last reply Reply Quote 0
        • JeGrJ
          JeGr LAYER 8 Moderator @frodet
          last edited by

          @frodet You have to fix your client configuration if you switch your server to use DCO.

          DCO automatically comes with a few drawbacks from the OpenVPN team (that are stated in the blog post Netgate published to DCO and the docu). E.g. AES-GCM is the only supported cipher (besides CHACHA20), compression is not available and mtu/mssfix/fragmentation settings aren't available.

          As your client sends AES-CBC that won't work, the other lines are most likely follow ups of the wrong cipher setting.

          Cheers

          Don't forget to upvote 👍 those who kindly offered their time and brainpower to help you!

          If you're interested, I'm available to discuss details of German-speaking paid support (for companies) if needed.

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