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    Setting VLAN MTU in GUI doesn't work?

    Scheduled Pinned Locked Moved L2/Switching/VLANs
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    • H
      highc
      last edited by

      Hi, it appears that setting a different (lower) MTU size for a VLAN than for the physical interface doesn't work in the GUI. It does work on the console, though.

      LAN (on LAGG0) with MTU size 9000.

      0_1532172667343_LAN.png

      VLAN70 (on LAGG0) with MTU size 1492

      0_1532172802789_VLAN70.png

      ifconfig on console after a reboot:

      0_1532172923217_console-lagg0.png
      0_1532172934047_console-lagg0_70.png

      After I run "ifconfig lagg0.70 mtu 1492" on the console, it looks ok:

      0_1532173128638_console-lagg0_70-2.png

      How can I make this persistent, if it's not working through the GUI, please?

      Thanks!

      pfSense+ 24.03 on Netgate SG-2100 (replaced SG-2440)
      pfSense 2.6 on Super Micro 5018D-FN4T (retired)

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      • H
        highc
        last edited by

        Sorry for pushing. Is this normal, did I miss anything, should I turn this into a bug report?

        Thanks.

        pfSense+ 24.03 on Netgate SG-2100 (replaced SG-2440)
        pfSense 2.6 on Super Micro 5018D-FN4T (retired)

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        • H
          hkjarral
          last edited by

          Seeing same issue with 2.4.4, setting mtu via gui does not work.

          JKnottJ 1 Reply Last reply Reply Quote 0
          • JKnottJ
            JKnott @hkjarral
            last edited by

            @hkjarral said in Setting VLAN MTU in GUI doesn't work?:

            Seeing same issue with 2.4.4, setting mtu via gui does not work.

            After setting the MTU, try testing to see if it actually changed. I suspect it hasn't. You can test by pinging with different size packets. So, you might set the VLAN MTU smaller and see if you can send the same size pings as over the native LAN.

            After you've done that, take a moment to think about what a VLAN actually is. With VLANs, you're just changing the contents of the Ethertype/length field, nothing more. The payload, as handled by the NIC, does not change.

            PfSense running on Qotom mini PC
            i5 CPU, 4 GB memory, 32 GB SSD & 4 Intel Gb Ethernet ports.
            UniFi AC-Lite access point

            I haven't lost my mind. It's around here...somewhere...

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            • H
              hkjarral
              last edited by

              I did, after setting from gui and applying changes, nothing changed on status > Interfaces page. Howerver doing it from CLI does the trick but I am not sure if it will survive reboot.

              Its not for any vlan its for two ports in a bridge, no vlan nothing.

              JKnottJ 1 Reply Last reply Reply Quote 0
              • JKnottJ
                JKnott @hkjarral
                last edited by

                @hkjarral said in Setting VLAN MTU in GUI doesn't work?:

                I did, after setting from gui and applying changes, nothing changed on status > Interfaces page. Howerver doing it from CLI does the trick but I am not sure if it will survive reboot.

                Does it actually change the MTU? As I mentioned, you can set it to something different than native and then try pinging with different size packets.

                When you create a VLAN, the VLAN tag is inserted ahead of the existing Ethertype/length field. It includes both the new Ethertype and length, along with priority. As a result the frame is now 4 bytes longer. That is all creating a VLAN does.

                PfSense running on Qotom mini PC
                i5 CPU, 4 GB memory, 32 GB SSD & 4 Intel Gb Ethernet ports.
                UniFi AC-Lite access point

                I haven't lost my mind. It's around here...somewhere...

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                • H
                  hkjarral
                  last edited by

                  It does not change the MTU thats what I am saying, I changed it in GUI and its still says 1500. There is no vlan involved here.

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