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    Windows Server DNS Server can't forward to pfSense

    DHCP and DNS
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    • bmeeksB
      bmeeks @netblues
      last edited by bmeeks

      @netblues:
      I think we are both saying the same thing but in a slightly different manner.

      I understood the OP to say that when he puts his upstream NAT gateway DNS server IP in the General Setup box on pfSense (that 192.168.101.2 address) that a DNS lookup performed directly on the pfSense console works. And when he removes that IP address and puts in nothing in the box, or else 127.0.0.1 to tell pfSense to use the localhost as the DNS server, his lookup fails. So in that first case, with an upstream DNS server listed in the General Setup tab for pfSense, dig will use that defined server to make DNS requests to. But if that General Setup tab DNS server IP box is blank (or points to 127.0.0.1), then dig will attempt to use unbound (the local resolver) for lookups.

      So to me that indicates that DNS Resolver on pfSense, when it is used and tries to contact the root servers, is unable to do so. Hence the "server fail" message. One reason this might be true is if some upstream network component (remember he described this as a lab VM setup) is restricting all DNS lookups to just that 192.168.101.2 server. So a rule upstream that says "if the destination for DNS port 53 traffic is not 192.168.101.2, then drop it" will cause DNS Resolver on pfSense to fail in contacting the root servers (and any other servers if you were to enable forwarding unless you forward only to the 192.168.101.2 box).

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      • N
        netblues @bmeeks
        last edited by netblues

        @bmeeks I have lab tested these scenarios. The only way to get a timeout- no servers can be reached, is by digging to an non existent dns server, or putting a firewall rule on dns.
        Everything else will be a case when unbound can BE reached.
        Yes, there are issues with the resolver setup and how it connects to the greater internet, but, the local timeout issue is something different.
        To sum it up.
        Unbound is running fine on 53, listening on all interfaces, and it cannot be contacted by dig or nslookup from pf cli using the lan ip of pf.
        No floating rules. And certainly this should work irrelevant of internet connectivity etc. This is where I start suspecting the vm/or the installation. Any ideas more than welcome.

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        • H
          Hekmil
          last edited by

          Ok so I fully understood what you both said.

          I can try make a fresh install with on a different machine to try out if it comes from the VM.

          I'll put nothing in the DNS Server boxes of the General Setup to try only using the unbound for lookups and set the pfSense to use DNS Resolver

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          • H
            Hekmil
            last edited by Hekmil

            So I did a fresh install.

            I can't check the box "Enable Forwarding Mode" in DNS Resolving tab if I don't specify one DNS Server in General Setup. On both install i get that

            Are you really sure I musn't had my NAT Gateway as a DNS server ? Because that's the only way I could resolve something, at least on the WAN interface. If I do that, i get the same error using the LAN ip address when using nslookup SERVFAIL
            Old and fresh install appear to have the same issue

            Also what's the difference between the DNS Resolving mode + "Enable Forwading Mode" enabled, and the DNS Forwarding mode ?

            Edit : With the DNS Resolver + Enable Forwarding Mode checked, I get this from the dig command (both install) :

            ; <<>> DiG 9.14.12 <<>> @172.16.1.2 cnn.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 3781
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;cnn.com.			IN	A

;; Query time: 84 msec
;; SERVER: 172.16.1.2#53(172.16.1.2)
;; WHEN: Thu Jul 23 13:35:05 CEST 2020
;; MSG SIZE  rcvd: 36

            I'm strill not getting why I can't resolve from a LAN interface

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            • N
              netblues @Hekmil
              last edited by

              @Hekmil Now that we have unbound (the pfsense dns resolver) talking to the world, we can move forward.

              The best is letting pfsense contact root servers and work the hierarchy until name resolution.
              This requires internet access to port 53 servers.
              If thats not the case, then you need to specify a forwarder.
              (as the webinterface dictates).

              The difference between resolver with forwarder and plain forwarder is local caching, negative caching, local names, dhcp integration, to name a few.
              dns forwarder is a rather old, solution to the same problem.

              Obviously your nat gateway is filtering dns requests, so using it is the only way to get dns to resolve.

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              • N
                netblues @Hekmil
                last edited by

                @Hekmil said in Windows Server DNS Server can't forward to pfSense:

                I'm strill not getting why I can't resolve from a LAN interface

                What do you mean ? dig says you can.

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                • H
                  Hekmil @netblues
                  last edited by Hekmil

                  @netblues yes dig says I can, but if I nslookup again from my lan IP I can't. Still getting the SERVFAIL.

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                  • N
                    netblues @Hekmil
                    last edited by

                    @Hekmil server fail means can't get response from upstream.
                    This is expected

                    Enable dns resolver forwading to your dns gateway and it will also work

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                    • H
                      Hekmil
                      last edited by

                      @netblues DNS Resolver Forwarding mode is enabled

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                      • N
                        netblues @Hekmil
                        last edited by netblues

                        @Hekmil and what do you have in system\general\dns ?

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                        • H
                          Hekmil @netblues
                          last edited by Hekmil

                          @netblues My NAT Gateway as DNS Server

                          The 2 boxes are checked. I've try to uncheck them to randomly test something but as expected nothing different

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                          • N
                            netblues @Hekmil
                            last edited by

                            @Hekmil dig @yournasip cnn.com
                            what happens?

                            H 1 Reply Last reply Reply Quote 0
                            • H
                              Hekmil @netblues
                              last edited by

                              @netblues With NAT ip address everything is fine, just switching to LAN ip won't make it

                              ; <<>> DiG 9.14.12 <<>> @192.168.101.2 cnn.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 63875
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 4, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; MBZ: 0x0005, udp: 4096
;; QUESTION SECTION:
;cnn.com.			IN	A

;; ANSWER SECTION:
cnn.com.		5	IN	A	151.101.129.67
cnn.com.		5	IN	A	151.101.65.67
cnn.com.		5	IN	A	151.101.193.67
cnn.com.		5	IN	A	151.101.1.67

;; AUTHORITY SECTION:
cnn.com.		5	IN	NS	ns-1086.awsdns-07.org.
cnn.com.		5	IN	NS	ns-1630.awsdns-11.co.uk.
cnn.com.		5	IN	NS	ns-47.awsdns-05.com.
cnn.com.		5	IN	NS	ns-576.awsdns-08.net.

;; Query time: 11 msec
;; SERVER: 192.168.101.2#53(192.168.101.2)
;; WHEN: Thu Jul 23 14:42:25 CEST 2020
;; MSG SIZE  rcvd: 236
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                              • N
                                netblues @Hekmil
                                last edited by

                                @Hekmil But you get server failed, not no servers can be reached, right?

                                ping -S 172.16.1.2 192.168.101.2 works?

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                                • H
                                  Hekmil @netblues
                                  last edited by Hekmil

                                  @netblues Yes I get Server can't find cnn.com : SERVFAIL

                                  No it doesn't ping, that might be a route issue no ?

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                                  • N
                                    netblues @Hekmil
                                    last edited by

                                    @Hekmil Do you have outbound nat enabled on your wan interface?

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                                    • H
                                      Hekmil @netblues
                                      last edited by

                                      @netblues Oh my god...

                                      The Outbound NAT configuration was set to automatic (which should have been enought right ?). So I tried to switch to manual and create a map ANY/ANY on WAN and everything works !

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                                      • N
                                        netblues @Hekmil
                                        last edited by

                                        @Hekmil Your configuration is not exactly typical and "automatic" things sometimes fail.
                                        From a technical point of view, pf being a router, you shouldn't need nat to reach an rfc1918 address.
                                        I suspect that packets reach your nas gateway, but never return.

                                        Most probably your nas gateway needs a route back for 172.16.1.0/24 pointing to your pfwan interface ip.
                                        Natting, (double) just makes the call originate from the wan interface.
                                        And connected networks don't need routes.

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                                        • H
                                          Hekmil @netblues
                                          last edited by

                                          @netblues Yes I also think it reachs the nat gateway considering the logs but never returning.

                                          I don't know how and where to set a route for my nat gateway though

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                                          • N
                                            netblues @Hekmil
                                            last edited by

                                            @Hekmil Maybe you can't. You have to figure this out
                                            In the mean time, stay with double nat.
                                            For simple internet connectivity and dns resolution it won't make any difference.

                                            H 1 Reply Last reply Reply Quote 0
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