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    WAN interfaces fail to return after power outage

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    • B
      bfeitell @stephenw10
      last edited by bfeitell

      @stephenw10

      Please see my post about a similar issue, and another thread I responded to. I think I know what is happening here, and it needs to be documented, and or added as a default setting in new installs.

      It seems that the dhclient code has been changed to respect the "interface-mtu" option that is being issued via DHCP by some CMTS equipment.

      I the cases I have seen the MTU is being set to 576, rather than being left at the pfSense default of 1500.

      In addition, the interface-mtu option issued via DHCP takes precedence over an MTU explicitly set by the user. To override the bad interface-mtu being set via DHCP, dhclient must be instructed to ignore the option. This is done by setting supersede interface-mtu 0 in the "Option modifiers" section of "Lease Requirements and Requests".

      When the MTU is set too small, it seems that DHCP renewals are failing. The failures coincide with errors like:
      arpresolve: can't allocate llinfo for $GATEWAY on $INTERFACE

      I think this is biting a lot of users on the upgrade to 2.4.4-RELEASE, and the symptoms are quirky. If left alone, the interface may stay up, but certain websites will become inaccessible due to packet fragmentation.

      PRIOR POSTS ON SAME SUBJECT:
      https://forum.netgate.com/topic/136089/solved-and-revised-2-4-4-release-arpresolve-can-t-allocate-llinfo-for-gateway-on-interface0-dhcp-mtu-576

      https://forum.netgate.com/topic/136253/frequent-internet-loss-need-help-figuring-out-where-and-why-maybe-pfsense-modem-isp-or-all-3

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      • stephenw10S
        stephenw10 Netgate Administrator
        last edited by stephenw10

        Wow, nice catch. And what are they doing sending 576?! 😕

        That does seem like it could be related at least. I'll be watching with anticipation...

        Steve

        1 Reply Last reply Reply Quote 0
        • stephenw10S
          stephenw10 Netgate Administrator
          last edited by

          Actually that should have been resolved already in https://redmine.pfsense.org/issues/8507

          If it does work that has somehow missed your install.

          Steve

          B 1 Reply Last reply Reply Quote 0
          • B
            bfeitell
            last edited by bfeitell

            From what I have read, I see references to the 576 MTU related to dialup connections. This might be an old fall-back that is being exposed only because dhclient now respects the option interface-mtu value being sent by the DHCP server. The value shows up in the issued lease. The changes in dhclient upstream are now exposing this.

            This is worth exploring in connection with reports of WAN interface disconnections, unpredictable website connectivity, and may affect things like name resolution. When combined with the "IP Do-Not-Fragment compatibility" option in System/Advanced/Firewall&NAT, the small MTU breaks connectivity with some websites. I saw problems with the iHeart Radio website and streams, and with loading newyorker.com. Please propagate this up the chain. My earlier post has links to the issues as they are discussed in the FreeBSD development system.

            https://forum.netgate.com/topic/136089/solved-and-revised-2-4-4-release-arpresolve-can-t-allocate-llinfo-for-gateway-on-interface0-dhcp-mtu-576

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            • B
              bfeitell @stephenw10
              last edited by bfeitell

              @stephenw10

              The fix discussed in Redmine doesn't seem to have made it into 2.4.4-RELEASE.

              Rather, the fix of using the patched version of dhclient now in the FreeBSD tree is that the user must issue "supersede interface-mtu 0" to ignore the requested option 26 information. Dhclient is still requesting option 26 info from the DHCP server. The patch allows being able to supersede option 26 as issued with the lease.

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              • B
                bfeitell
                last edited by

                I have opened a Redmine account, and posted in the relevant thread.

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                • stephenw10S
                  stephenw10 Netgate Administrator
                  last edited by

                  I agree, it's certainly worth exploring. It could explain a number of threads here.

                  The value supersede interface-mtu 0 should be in the dhclient conf files in /var/etc by default. It is on everything I've just checked. If some connections are still seeing a 576 MTU then there must be some combination of factors that prevent it being added. If that is the case we need to find out what they are and stop that happening.

                  Steve

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                  • B
                    bfeitell
                    last edited by

                    I have a sneaking suspicion that a prior manual setting of MTU on the interface may be interfering with the the setting of supersede interface-mtu 0 in dhclient.conf on upgrade. I know that I have previously hard set the MTU to 1500 on a number of boxes as a matter of course. In this instance, the hard set MTU will not be respected if supersede interface-mtu 0 is not making it into dhclient.conf.

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                    • stephenw10S
                      stephenw10 Netgate Administrator
                      last edited by

                      I think you're right. Working on something now....

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                      • B
                        bfeitell
                        last edited by

                        Jim Pingle, the developer working on this has entered a new diff. Apparently, checking the advanced options checkbox and then saving and applying the config with no other changes entered, and then upgrading to 2.4.4-RELEASE, is enough to disrupt the fix the developers had put in place for the option 26 interface-mtu bug introduced by the new dhclient.

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                        • jimpJ
                          jimp Rebel Alliance Developer Netgate
                          last edited by

                          I added a new note with a workaround to the Upgrade Guide: https://www.netgate.com/docs/pfsense/install/upgrade-guide.html#upgrading-from-versions-older-than-pfsense-2-4-4

                          A patch is available that can be added with the System Patches package.

                          The fix is discussed on https://redmine.pfsense.org/issues/8507

                          Remember: Upvote with the 👍 button for any user/post you find to be helpful, informative, or deserving of recognition!

                          Need help fast? Netgate Global Support!

                          Do not Chat/PM for help!

                          1 Reply Last reply Reply Quote 1
                          • B
                            bfeitell
                            last edited by

                            Thank you! This is wonderful.

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                            • B
                              bfeitell
                              last edited by bfeitell

                              I think this bug also applies to fresh installs using a restored config, not just on in-place upgrades. That is the case for the system I encountered this on.

                              jimpJ 1 Reply Last reply Reply Quote 0
                              • jimpJ
                                jimp Rebel Alliance Developer Netgate @bfeitell
                                last edited by

                                @bfeitell said in WAN interfaces fail to return after power outage:

                                I think this bug also applies to fresh installs using a restored config, not just on in-place upgrades. That is the case for the system I encountered this on.

                                Since it is a setting in the configuration and not a problem on the filesystem, that is correct. If you restore a config with advanced or custom options set there, it would fail this way.

                                Remember: Upvote with the 👍 button for any user/post you find to be helpful, informative, or deserving of recognition!

                                Need help fast? Netgate Global Support!

                                Do not Chat/PM for help!

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                                • B
                                  bfeitell
                                  last edited by

                                  It is an insidious bug. I triggered the DHCP renewal problems by saving and applying on the WAN with or without changes. Unless triggered by the user, it will lurk until the next DHCP renewal fails, and that may not happen for 30 minutes or more. Looking through recent forum posts, I suspect this bug is in play whenever a user notices arpresolve: can't set llinfo for $GATEWAY on $INTERFACE errors.

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                                  • P
                                    peter_richardson
                                    last edited by

                                    Okay so it went a bit over my head there. Can someone please break it down for me? Where are we up to with this one? Is there a patch? Or a configuration change is needed?

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                                    • stephenw10S
                                      stephenw10 Netgate Administrator
                                      last edited by

                                      First try just adding the following to the option modifiers field in the advanced section of the dhcp setup on WAN. Check the 'Advanced Configuration' box to see that field if it's not already.
                                      supersede interface-mtu 0

                                      If that works then you can try the patch instead. That would be a helpful test for us.

                                      Steve

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                                      • P
                                        peter_richardson
                                        last edited by peter_richardson

                                        Hey Steve, okay I tried it (see screenshot) but didn't change anything. System log didn't report any errors this time though.2_1538947004879_Screenshot_20181008-080516.png 1_1538947004850_Screenshot_20181008-080614.png 0_1538947004779_Screenshot_20181008-080428.png I didn't have the WWAN connected this time so that's why it's not showing up. To get the WAN connection going again after power out, I need to either unplug the Ethernet cable and re plug, or disable and re enable the interface, or make some change in the WAN interface and save.

                                        1 Reply Last reply Reply Quote 1
                                        • stephenw10S
                                          stephenw10 Netgate Administrator
                                          last edited by

                                          Hmm, no 'arpresolve' errors though?

                                          Did you ever try running ifconfig -av during the working and non-working states to compare them?

                                          Steve

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                                          • P
                                            peter_richardson
                                            last edited by

                                            Did you see the above images? One of them is of the syslog while it was happening after putting in the string into the Option Modifiers field.

                                            Yes I did, but it's on my other computer, I'll paste it here later.

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