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  • NSLOOKUP server "unknown"

    When I try to do a lookup from my SBS2008 server it always says server "unknown". Make note that I"m looking up internal IPs. I have a PTR record as well as a reverse lookup.

    If try the same lookups form my 2nd DNS server it doesn't give any "unknown" and states the name of that server as expected.

    I've done some reading on this topic and see no answer that applies. I'm not saying it's a concern...but I've never experienced this before on any DNS server.
    Attached Files

  • #2
    Re: NSLOOKUP server "unknown"

    Are you using IPV6 in your network, if yes is PTR for IPV6 created?
    Cheers!!
    MCSE 2003,MCSA- Messaging 2003, VCP

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    • #3
      Re: NSLOOKUP server "unknown"

      I did not knowingly create IPV6 as our network is small (40 clients).

      This is a default install of SBS2008. So does it create IPV6 then? Is the fact the "address" for the server is hex mean that it's a IPV6 address in any way? As I've designated it with IPV4 10.0.0.2.

      I know little of IPV6 since we have no need to implement it, but have wonderered why many different address references are returned in the the hex shown and not the standard IP numeric I"m used to.

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      • #4
        Re: NSLOOKUP server "unknown"

        Open up a cmd window

        ipconfig /all > c:\ipconfig.txt

        Attach the ipconfig.txt from the root of C:\ to a post here and we can probably figure out the problem.
        TIA

        Steven Teiger [SBS-MVP(2003-2009)]
        http://www.wintra.co.il/
        sigpic
        Iím honoured to have been selected for the SMB 150 list for 2013. This is the third time in succession (no logo available for 2011) that I have been honoured with this award.

        We donít stop playing because we grow old, we grow old because we stop playing.

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        • #5
          Re: NSLOOKUP server "unknown"

          I've attached a screenshot. My guess is the answer is "yes".

          Rather then try to remove IPV6 as I'm not sure why SBS2008 setup this server default with this, but would fear it may be needed for Exchange...would simply adding a PTR record with that IPV6 address solve the issue then? or do I need some other configs?

          On a 2nd note how the heck are you guys remembering these link hex addresses for daily management of networks! I figured IPV6 was only for internet needs and not LAN.

          thanks.
          Attached Files

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          • #6
            Re: NSLOOKUP server "unknown"

            SBS2008 automatically configures the TCP/IP properties of the NIC with an IPv6 address and also configures the DNS server to listen on all ip addresses including the IPv6 addresses. You should not disable IPv6 on SBS2008. The message you get when running nslookup is because the nslookup program uses the local DNS client settings (remember that the DC is a DNS client as well as a DNS server but these two components are not related to each other). The fact that you get a "server unknown" message is because you don't have an IPv6 reverse zone setup. This is the same as with IPv4 if you don't have an IPv4 reverse zone set up. You can safely ignore the message as an IPv4 or IPv6 reverse zone isn't required for the proper operation of the DC\DNS server.

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            • #7
              Re: NSLOOKUP server "unknown"

              Great info Joe, but it begs my brain with a few additional questions then....

              So why would SBS2008 setup both IPV4 and IPV6 and create a reverse lookup for IPv4 and NOT IPV6? Doesn't seem logical to me!

              The reason I tested an NSLOOKUP on that server was the fact we saw in the header of internal emails the items highlighted in the attached screenshot. We are seeing that some internal emails are getting dropped in spam folders although all the spam tagging is showing no violation. My only thought was the concern that references a concern with a TEMPERROR and specifically with SPF that there is a DNS timeout.

              I'm always amazed that how a default install of an SBS2008 product can present so many challenges and thus I'm ( a layperson) trying to figure out if the DNS timeout (for internal traffic) is related to the NSLOOKUP observations I've made.

              Obviously not knowing enough info allows my imagination to run wild that somehow these are related.
              Attached Files

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              • #8
                Re: NSLOOKUP server "unknown"

                I don't think SBS does create an IPv4 reverse lookup zone automatically, does it? I've never noticed that and I'm pretty sure I've had to set it up for myself.

                That being said, the lack of an internal IPv6 reverse lookup zone shouldn't have any bearing on emails being flagged as spam or the failure to do a PTR or SPF lookup. THE PTR and SPF lookups will be performed for the external DNS namespace and ip address block, not the internal ones.

                I can't really follow the screenshot. Is that from your server trying to send an external email and failing on finding the SPF or PTR for the recipient's domain?

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                • #9
                  Re: NSLOOKUP server "unknown"

                  Originally posted by joeqwerty View Post

                  I can't really follow the screenshot. Is that from your server trying to send an external email and failing on finding the SPF or PTR for the recipient's domain?
                  This is the header of an email getting tagged as spam. This email is generated on a webserver external to our facility and comes in the door. We created the user called [email protected] but for some reason the server says no dice.

                  Although this email is generated by another server we used this trick for years so that the server would know it belonged. I think the newer system identifies the external IP as not internal and thus tags it (inconsistently) as spam via SPF (just grasping here. Where this worked in the past it appears to not work now.

                  I think you did a great job of enlightening to me about IPV6 and that my comments and concerns are unrelated to one another. Thanks.

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                  • #10
                    Re: NSLOOKUP server "unknown"

                    Glad to help.

                    I did notice in the screenshot that the web server seems to be connecting as 127.0.0.1 in it's HELO command. Could that be part of the problem? Shouldn't it be connecting as it's external ip address?

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