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[RESOLVED]No internet on ubuntu when disable dhcp

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  • F
    Farisse
    last edited by Jul 11, 2020, 12:37 PM

    Update !

    So i reinstalled my ubuntu machine and deactivated netplan and ... It didn't work.

    The simple reason is, i am working on a private network they have their own DNS servers.

    So when i am using the DHCP server there is apparently an automatic DNS forwarding to my machine. The DNS of my school but its hidden in the ubuntu settings. (ofc)

    So now when i tried to put the dns of my school in my /etc/systemd/resolved.conf document. It worked.

    Now i'm wondering if you may help me to understand how i could make it work without adding the dns of my school in the /resolved.conf ?

    I thought about dns forwarding, but not sure about the working.

    If someone can help it would be great. If not, moderator can close the subject and mark it as solved.

    Thank you for your help ! :)

    Farisse

    B 1 Reply Last reply Jul 11, 2020, 1:26 PM Reply Quote 0
    • B
      bmeeks @Farisse
      last edited by bmeeks Jul 11, 2020, 1:28 PM Jul 11, 2020, 1:26 PM

      @Farisse said in No internet on ubuntu when disable dhcp:

      Update !

      So i reinstalled my ubuntu machine and deactivated netplan and ... It didn't work.

      The simple reason is, i am working on a private network they have their own DNS servers.

      So when i am using the DHCP server there is apparently an automatic DNS forwarding to my machine. The DNS of my school but its hidden in the ubuntu settings. (ofc)

      So now when i tried to put the dns of my school in my /etc/systemd/resolved.conf document. It worked.

      Now i'm wondering if you may help me to understand how i could make it work without adding the dns of my school in the /resolved.conf ?

      I thought about dns forwarding, but not sure about the working.

      If someone can help it would be great. If not, moderator can close the subject and mark it as solved.

      Thank you for your help ! :)

      Farisse

      It is a fairly common practice for schools to intercept DNS requests and redirect/force them to a school-maintained DNS server. The school's DHCP server is giving all machines on the network the proper DNS server to use. This is done to monitor for and/or prevent access to inappropriate content. It also allows the school to have DNS entries they maintain for local servers and services. If your school network is doing this, then you won't be able to use another DNS server unless you perhaps can get something running over a VPN.

      F 1 Reply Last reply Jul 11, 2020, 3:06 PM Reply Quote 1
      • F
        Farisse @bmeeks
        last edited by Jul 11, 2020, 3:06 PM

        @bmeeks
        Thank you for your answer
        Indeed, i have to use the dns of the school. But what i don't understand is, i don't put anything on my windows machine except the static ip, gateway that's all and it works. But on my ubuntu machine it doesn't work. So i don't understand how it works in pfsense to let my windows machine use the dns i entered in pfsense and not my ubuntu machine. It's not logic for me :/

        B 1 Reply Last reply Jul 11, 2020, 3:19 PM Reply Quote 0
        • B
          bmeeks @Farisse
          last edited by Jul 11, 2020, 3:19 PM

          @Farisse said in No internet on ubuntu when disable dhcp:

          @bmeeks
          Thank you for your answer
          Indeed, i have to use the dns of the school. But what i don't understand is, i don't put anything on my windows machine except the static ip, gateway that's all and it works. But on my ubuntu machine it doesn't work. So i don't understand how it works in pfsense to let my windows machine use the dns i entered in pfsense and not my ubuntu machine. It's not logic for me :/

          Is your Windows machine a member of an AD domain? If so, the AD domain controller is the DNS server, and it probably forwards to the school's DNS server (or it may actually be the school's DNS server).

          F 1 Reply Last reply Jul 11, 2020, 4:00 PM Reply Quote 0
          • F
            Farisse @bmeeks
            last edited by Jul 11, 2020, 4:00 PM

            @bmeeks Nope its not :(
            I just tried but my windows machine is not member of AD domain.
            here is a little video : https://streamable.com/6mznjo
            even with the schools dns it doesn't work anymore. Really strange things are happening here :/

            B 1 Reply Last reply Jul 11, 2020, 4:04 PM Reply Quote 0
            • B
              bmeeks @Farisse
              last edited by Jul 11, 2020, 4:04 PM

              @Farisse said in No internet on ubuntu when disable dhcp:

              @bmeeks Nope its not :(
              I just tried but my windows machine is not member of AD domain.
              here is a little video : https://streamable.com/6mznjo
              even with the schools dns it doesn't work anymore. Really strange things are happening here :/

              I am not a user of Hyper-V. I am an ESXi user. One place I would concentrate my research is within the networking configuration of Hyper-V.

              Are you running Hyper-V on hardware by itself, or are you running Hyper-V on say a Windows desktop? There will be substantial changes to some of the networking in one installation versus the other.

              F 1 Reply Last reply Jul 11, 2020, 4:14 PM Reply Quote 0
              • F
                Farisse @bmeeks
                last edited by Jul 11, 2020, 4:14 PM

                @bmeeks
                I don't think the problem should come from the hyper v configuration. I think this because all the other machines are working, and its only ubuntu machines that doesn't work. (Maybe i should go to an ubuntu forum sorry for that). I work on a windows desktop.
                So i have a VPN connection to the windows machine where is installed windows server and hyper-v manager.
                I think the problem should be something like resolving he dns between the ubuntu machine and pfsense but idk where to search :/

                1 Reply Last reply Reply Quote 0
                • F
                  Farisse
                  last edited by Jul 11, 2020, 11:38 PM

                  After a lot of research i'm asking myself if someone could maybe tell me where i could find any information about the changes that are made when the dhcp server is enabled.

                  I searched in the pfsense book, but it is not written how it works. If i find what changes are made i would be able to find where the problem is with my server.

                  Thank you guys !

                  1 Reply Last reply Reply Quote 0
                  • J
                    johnpoz LAYER 8 Global Moderator
                    last edited by Jul 12, 2020, 12:27 AM

                    And again - The dhcp server being on or off has ZERO to do with whatever issue your having.

                    The only changes that happen that you might not see when you enable a dhcp server on a specific interface, is some hidden rules get added to allow for dhcp to reach the server running on pfsense..

                    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 2.7.2, 24.11

                    F 1 Reply Last reply Jul 12, 2020, 12:05 PM Reply Quote 0
                    • B
                      bmeeks
                      last edited by bmeeks Jul 12, 2020, 1:21 AM Jul 12, 2020, 1:19 AM

                      Okay, going back and reading your original post one more time, this is what I am hearing you say:

                      When you turn on or enable the DHCP server in pfSense and you enable DHCP in your Ubuntu machine, you have Internet access. But when you turn off the DHCP server in pfSense and try a static IP with no DHCP configured in Ubuntu, you have no Internet access.

                      If the above is correct, then this is what I think is happening. You are never actually disabling the DHCP client on the Ubuntu machine even though you might think you are. So when you turn off the DHCP server in pfSense, the DHCP client on Ubuntu can't get a proper IP address and thus you have no connectivity. With the DHCP server running on pfSense, the Ubuntu DHCP client can get the info it needs and the Internet works on the Ubuntu machine.

                      That's what I believe is happening. You think you are turning off DHCP on the Ubuntu machine and switching to a static IP, but I'm thinking perhaps you are not actually doing that. I know that it can be a real pain to re-plumb the network in modern Linux distros with their fancy GUIs. They really, really want to use the DHCP client.

                      1 Reply Last reply Reply Quote 0
                      • F
                        Farisse @johnpoz
                        last edited by Jul 12, 2020, 12:05 PM

                        @johnpoz You are right, but where could i find these rules ? My firewall rules are empty (or everything is open). There is something i am missing in this configuration. It makes me sick of not understanding why sometimes it works and sometimes not with the same configuration.

                        @bmeeks i actually don't even know when it's working or not. I had a few minutes ago an internet connection on my machine and, a few minutes later nothing anymore.

                        How could i get more details about this ? Logs ?

                        J 1 Reply Last reply Jul 12, 2020, 12:30 PM Reply Quote 0
                        • J
                          johnpoz LAYER 8 Global Moderator @Farisse
                          last edited by Jul 12, 2020, 12:30 PM

                          @Farisse said in No internet on ubuntu when disable dhcp:

                          My firewall rules are empty (or everything is open)

                          If your firewall rules are EMPTY then everything is blocked!

                          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 2.7.2, 24.11

                          F 1 Reply Last reply Jul 12, 2020, 12:46 PM Reply Quote 0
                          • F
                            Farisse @johnpoz
                            last edited by Jul 12, 2020, 12:46 PM

                            @johnpoz No sorry I mean everything is open 74ea0f9a-a7ef-4ac7-bcc2-c1b7bf11f7ec-image.png

                            1 Reply Last reply Reply Quote 0
                            • J
                              johnpoz LAYER 8 Global Moderator
                              last edited by johnpoz Jul 12, 2020, 12:49 PM Jul 12, 2020, 12:47 PM

                              And clearly you have 13 states currently open using that rule, and have moved 63.18 MB of traffic.

                              How about some actual info... Lets see you ping the DMZ address from this client.. Lets see you do a dns query to what the dmz address, some other dns server?

                              Lets see the ifconfig output from this client. When you say it doesn't work, and then when you say it works if you turn on dhcp on pfsense.

                              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 2.7.2, 24.11

                              F 1 Reply Last reply Jul 12, 2020, 1:02 PM Reply Quote 0
                              • F
                                Farisse @johnpoz
                                last edited by Jul 12, 2020, 1:02 PM

                                @johnpoz said in No internet on ubuntu when disable dhcp:

                                How about some actual info... Lets see you ping the DMZ address from this client.. Lets see you do a dns query to what the dmz address, some other dns server?
                                Lets see the ifconfig output from this client. When you say it doesn't work, and then when you say it works if you turn on dhcp on pfsense.

                                i am not sure about understanding the questions do you mean that i show the results of the commands you said ?

                                There are 2 dns servers. One one the schools network and the other in my lan network.

                                1 Reply Last reply Reply Quote 0
                                • J
                                  johnpoz LAYER 8 Global Moderator
                                  last edited by johnpoz Jul 12, 2020, 1:09 PM Jul 12, 2020, 1:05 PM

                                  Yes lets see the output of the commands.. Not just you saying something doesn't work via what a browser? ping pfsense dmz address, if you can't then your never getting anywhere.. If you can not query dns then your never going to get anywhere via fqdn.

                                  Lets see say a traceroute when it works, and when it doesn't work to both an IP say 8.8.8.8 and then say via a fqdn like www.google.com

                                  Your not doing something like static arps are you in pfsense?

                                  If you setup a static arp say for 1.2.3.4 mac xyz so that what the client gets when dhcp is on, and then you setup IP on the machine to be 1.2.3.5 then no it wouldn't work.

                                  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 2.7.2, 24.11

                                  F 1 Reply Last reply Jul 12, 2020, 1:17 PM Reply Quote 0
                                  • F
                                    Farisse @johnpoz
                                    last edited by Farisse Jul 12, 2020, 1:30 PM Jul 12, 2020, 1:17 PM

                                    @johnpoz
                                    the video is uploading i'll add screenshots in a few minutes
                                    https://streamable.com/j30bzs

                                    Ping from Windows Hyper-v to DMZ network 455fbd6a-2e49-4aca-9c16-51e06309c41e-image.png

                                    Ping from Ubuntu to DNS/DMZ network + ifconfig
                                    41793422-93b4-41ea-b546-d88f9cc70877-image.png

                                    Do you need more info ?

                                    1 Reply Last reply Reply Quote 0
                                    • J
                                      johnpoz LAYER 8 Global Moderator
                                      last edited by Jul 12, 2020, 2:05 PM

                                      And that is with dhcp or static? And where is your dns query?

                                      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 2.7.2, 24.11

                                      1 Reply Last reply Reply Quote 0
                                      • F
                                        Farisse
                                        last edited by Farisse Jul 12, 2020, 2:17 PM Jul 12, 2020, 2:17 PM

                                        This is Static the video is when internet was functional and then after reboot ... nothing anymore

                                        here is the dns query:
                                        c3cd78d9-8c96-438e-890e-4835863518f0-image.png

                                        1 Reply Last reply Reply Quote 0
                                        • J
                                          johnpoz LAYER 8 Global Moderator
                                          last edited by johnpoz Jul 12, 2020, 3:53 PM Jul 12, 2020, 3:45 PM

                                          Well not really possible to use the internet without dns resolution..

                                          What server are you trying to query - can not tell from that command..

                                          Do a dig with with @ipaddress of dns server.

                                          something like dig @192.168.1.1 www.google.com

                                          your command is just going to ask some dns server, which don't know what that is for 192.168.1.1

                                          Is pfsense listening on dmz interface for dns? Are you pointing dns to something else?

                                          how about this output

                                          networkctl status
                                          ●        State: routable
                                                 Address: 192.168.2.12 on ens3
                                                          fe80::11:32ff:fe22:cc7d on ens3
                                                 Gateway: 192.168.2.253 (ADI Engineering, Inc.) on ens3
                                                     DNS: 192.168.3.10
                                          Search Domains: local.lan
                                                     NTP: 192.168.3.32
                                                          192.168.2.253
                                          

                                          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 2.7.2, 24.11

                                          F 1 Reply Last reply Jul 12, 2020, 4:02 PM Reply Quote 0
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