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    Not able to connect to some website

    Scheduled Pinned Locked Moved IPv6
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    • nonickN
      nonick @Jeff_WuYo
      last edited by nonick

      @jeff_wuyo The maximum MTU for WAN-Interface is 1500 bytes (Ethernet maximum MTU size). With PPPoE connections, the PPPoE header increases the frame size by 8 bytes, so must lower the MTU to 1492.
      You can test it with it, if it still doesn't work then set the MSS value additionally to 1452 or 1432.

      Netgate 6100

      J JKnottJ 2 Replies Last reply Reply Quote 0
      • J
        Jeff_WuYo @nonick
        last edited by Jeff_WuYo

        @nonick

        Nope, didn't work. I set MTU to 1492 on WAN, MyPC just falls back to IPv4. Pure IPv6 site e.g. v6.facebook.com just can't connect. I can't ping using IPv6. Setting MSS to 1452 or 1432 doesn't help either.
        Here's some test I run.
        2f22396e-e582-48f7-8095-6cd6b4eb40ad-image.png
        bdd59188-3e2c-48db-b6bc-963991853c07-image.png
        4583c4c7-dbac-464f-81b4-e64555acb08e-image.png

        @nonick said in Not able to connect to some website:

        The maximum MTU for WAN-Interface is 1500 bytes

        If that's so, why am I seeing package length way over 1500 when I setup my network as Modem/Router? Is wireshark just showing sum of multiple packages? (I should mention the Modem/Router is provided by my ISP, it's using PPPoE as well.) Here is an example.
        81e67729-4a47-44c7-b95c-4e5e61b12c50-image.png

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        • johnpozJ
          johnpoz LAYER 8 Global Moderator @Jeff_WuYo
          last edited by

          @jeff_wuyo said in Not able to connect to some website:

          I set my MTU 6000 on both WAN and LAN.

          Well no wonder your having issues.. That is just borked..

          An intelligent man is sometimes forced to be drunk to spend time with his fools
          If you get confused: Listen to the Music Play
          Please don't Chat/PM me for help, unless mod related
          SG-4860 24.11 | Lab VMs 2.8, 24.11

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          • JKnottJ
            JKnott @Jeff_WuYo
            last edited by

            @jeff_wuyo said in Not able to connect to some website:

            I set my MTU 6000 on both WAN and LAN.

            While you can do what you want on your own LAN, you should go with what your ISP requires on the WAN side.

            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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            • JKnottJ
              JKnott @nonick
              last edited by

              @nonick said in Not able to connect to some website:

              (Ethernet maximum MTU size)

              Not any more. That ended with frame expansion in the late '90s and these days jumbo frames of several KB are possible.

              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...

              johnpozJ nonickN 2 Replies Last reply Reply Quote 0
              • johnpozJ
                johnpoz LAYER 8 Global Moderator @JKnott
                last edited by johnpoz

                @jknott said in Not able to connect to some website:

                jumbo frames of several KB are possible.

                While this is true - I highly doubt all his devices on his lan are using jumbo of 6000.. Devices like printer and for sure any iot normally have zero support for jumbo.

                And typical nics/drivers support only a couple of sizes..

                jumbo.jpg

                What I will say is pulling some arbitrary number like 6000 out of the air and setting your mtu to that is going to cause you grief that is for sure..

                An intelligent man is sometimes forced to be drunk to spend time with his fools
                If you get confused: Listen to the Music Play
                Please don't Chat/PM me for help, unless mod related
                SG-4860 24.11 | Lab VMs 2.8, 24.11

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

                  @jknott said in Not able to connect to some website:

                  Not any more. That ended with frame expansion in the late '90s and these days jumbo frames of several KB are possible.

                  That's right, I wrote on the WAN interface. 😉

                  The maximum MTU for WAN-Interface is 1500 bytes

                  Netgate 6100

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                  • JKnottJ
                    JKnott @johnpoz
                    last edited by

                    @johnpoz

                    If one sets a DHCP server to provide whatever MTU size, wouldn't the device accept that value? I know there will be issues with WiFi. BTW, I've been around long enough to remember when 576 was a common MTU size.

                    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...

                    johnpozJ 1 Reply Last reply Reply Quote 0
                    • johnpozJ
                      johnpoz LAYER 8 Global Moderator @JKnott
                      last edited by

                      @jknott said in Not able to connect to some website:

                      provide whatever MTU size, wouldn't the device accept that value?

                      No there is nothing saying they would even look or accept such values. Look at windows and search domain as perfect example. So option 119 of dhcp allows for assigning search domains, but not until windows 10 in a later build did windows accept such an option.

                      Just because dhcp server offers the ability to hand out some option, doesn't mean clients would request or even accept an option. And stuff like iot devices normally have base min to "work" in their network stack anyway..

                      Using non standard frame sizes is something that can really mess up a network if not all the devices are setup and validated to use and understand these non standard frame sizes. Just because say the switch will pass them, doesn't mean the device is smart enough to leverage or use them..

                      And sure and the hell wouldn't use 6000?

                      Can pretty much promise you issues he is seeing is related to such settings.. If anything PPPoE connection most likely would want something lower than the standard 1500 because of the overhead..

                      I would suggest he moves his lan back to 1500, and then get with his ISP for the proper setup for his wan connection.. A common pppoe mss clamp size is like 1452.. But for optimal working with his ISP he should contact them for proper setup.

                      An intelligent man is sometimes forced to be drunk to spend time with his fools
                      If you get confused: Listen to the Music Play
                      Please don't Chat/PM me for help, unless mod related
                      SG-4860 24.11 | Lab VMs 2.8, 24.11

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                      • J
                        Jeff_WuYo
                        last edited by Jeff_WuYo

                        After I reset pfSense, and did a new setup, the issue still remain. I can't connect to archlinux.org via IPv6.

                        @johnpoz said in Not able to connect to some website:

                        I would suggest he moves his lan back to 1500, and then get with his ISP for the proper setup for his wan connection.. A common pppoe mss clamp size is like 1452.. But for optimal working with his ISP he should contact them for proper setup.

                        I agree, I should consult my ISP for help. I left MTU and MSS default. Will it related to PMTUD no working? The last result might be using pfSense in transparent mode. I've never tested it yet.

                        Another issue is ICMP req always failed (tested using ipv6-test.com), even I allow it on WAN interface. This didn't happen on my last configuration, which is pretty much the same as this one except I left DHPCv6 enable. I think I disable DHCPv6 last time, MyPC use RDNSS instead. I'm scratching my head off.

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