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  • DHCP not leasing in his own subnet

    Hi All,

    Kind of a weird problem here.
    We needed to move the DHCP service from an ancient NT4 server to a Windows Server 2003 server for obvious reasons.

    The Active Directory based environment consists of a network with multiple VLAN 's.
    The IP-Helper is configured correctly on all of them, except on the vlan where the DHCP server is in.
    The DHCP Server is authorised in AD, and is working perfectly for all his scopes (29) except for the scope that is supposed to provide IP's in his own subnet.

    So, the servers IP is 172.23.14.21/24
    And the scope is from 172.23.14.35 to 172.23.14.64

    And none of the DHCP clients located in the 172.23.14.x VLAN is receiving a DHCP lease.

    I realy have no clue how to troubleshoot this since the DHCP server is leasing IPs in all other VLAN's.

    Anybody an idea?

    Thanks in advance...
    Last edited by SaMaLaKo; 22nd May 2008, 13:40. Reason: Additional info
    Semper in faecibus sumus, sole profundum variat

  • #2
    Re: DHCP not leasing in his own subnet

    Additional question.
    would it make sence to disconnect the DHCP server from the network and put it on a hub together with a DHCP client?
    Just to test if the network is the cause of this problem?

    Does the DHCP server allways need a DC to check if it is authorised, or only when the DHCP service is started?
    Last edited by SaMaLaKo; 22nd May 2008, 14:02. Reason: typo
    Semper in faecibus sumus, sole profundum variat

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    • #3
      Re: DHCP not leasing in his own subnet

      I'm not going to explain the Authorisation process as MS already done it (and probebly a lot better than i could). But i advice you to read this link to understand the Authorization process.

      http://technet2.microsoft.com/window....mspx?mfr=true

      Regards to the issue you are having,
      Have you checked the DHCP log?
      &systemroot&\system32\DHCP

      Is the "home" scope active?
      Last edited by Killerbe; 22nd May 2008, 16:11.
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      • #4
        Re: DHCP not leasing in his own subnet

        Do you have a DHCP relay or DHCP Helper setup for this VLAN???

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        • #5
          Re: DHCP not leasing in his own subnet

          @wullieb1
          Originally posted by SaMaLaKo View Post
          ...
          The Active Directory based environment consists of a network with multiple VLAN 's.
          The IP-Helper is configured correctly on all of them, except on the vlan where the DHCP server is in.
          ...
          So no, not for this VLAN, all the other ones have an IP helper configured on the switches.

          @Killerbe
          yup, the home scope is active.
          And I checked the DHCP log, but can't find anything there.
          I searched the logs for a MAC of one of the clients in the 'Home' scope but it isn't listed.

          @All
          I know the DHCP discovers are reaching the DHCP server (you can monitor this by configuring a performance counter in PerfMon).

          But I'm not sure if the DHCP offer reaches the DHCP client.

          Does somebody know a tool to test the DHCP communication between client and server? Something like IPNetMonitorX but for windows...
          Semper in faecibus sumus, sole profundum variat

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          • #6
            Re: DHCP not leasing in his own subnet

            You could use wireshark or wincap to capture traffic from one of the clients and filter out UDP.

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            • #7
              Re: DHCP not leasing in his own subnet

              What does the system event viewer of the clients tell you?
              Propably only event 1007, but its worth a try.
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              • #8
                Re: DHCP not leasing in his own subnet

                Originally posted by Killerbe View Post
                What does the system event viewer of the clients tell you?
                Propably only event 1007, but its worth a try.
                Only event 1020 mentioning some other scopes are running out of addresses to lease...
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                • #9
                  Re: DHCP not leasing in his own subnet

                  Have you tried to reconciled that scope?

                  What happend to the old DHCP?
                  [Powershell]
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                  • #10
                    Re: DHCP not leasing in his own subnet

                    I would put WireShark or Microsoft Network Monitor 3 on the client and server and start a capture filtering for DHCP, then run ipconfig/renew on the client and see what both captures show.

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                    • #11
                      Re: DHCP not leasing in his own subnet

                      Check to make sure the dhcp server has the correct bindings (in DHCP snap-in, right-click server -> Properties -> Advanced -> Bindings)

                      You also might want to check the firewall or AV to make sure it's not blocking the discover packets. (are you using SEP with all those extra components installed?) IIRC, DHCP relays use unicast whereas if there's no relay the DHCP server receives a broadcast.

                      Originally posted by SaMaLaKo View Post
                      I know the DHCP discovers are reaching the DHCP server (you can monitor this by configuring a performance counter in PerfMon).

                      But I'm not sure if the DHCP offer reaches the DHCP client.
                      You should be able to see if the server is sending out the offer using netmon or wireshark on the server.
                      Regards,
                      Jeremy

                      Network Consultant/Engineer
                      Baltimore - Washington area and beyond
                      www.gma-cpa.com

                      Comment


                      • #12
                        Re: DHCP not leasing in his own subnet

                        Originally posted by joeqwerty View Post
                        I would put WireShark or Microsoft Network Monitor 3 on the client and server and start a capture filtering for DHCP, then run ipconfig/renew on the client and see what both captures show.
                        I was already on this, this is the result I get when performing a repair on the NIC:

                        On my client (with wireshark)
                        Source Destination Protocol Info
                        0.0.0.0 255.255.255.255 DHCP DHCP Discover - Transaction ID 0x8d445f96
                        0.0.0.0 255.255.255.255 DHCP DHCP Discover - Transaction ID 0x8d445f96
                        0.0.0.0 255.255.255.255 DHCP DHCP Discover - Transaction ID 0x8d445f96
                        0.0.0.0 255.255.255.255 DHCP DHCP Discover - Transaction ID 0x8d445f96
                        0.0.0.0 255.255.255.255 DHCP DHCP Discover - Transaction ID 0xb59ef5c2
                        0.0.0.0 255.255.255.255 DHCP DHCP Discover - Transaction ID 0xb59ef5c2
                        0.0.0.0 255.255.255.255 DHCP DHCP Discover - Transaction ID 0xb59ef5c2
                        0.0.0.0 255.255.255.255 DHCP DHCP Discover - Transaction ID 0xb59ef5c2

                        On the server (with Network Monitor)
                        Source Destination Protocol Description
                        0010C6E15021 *BROADCAST DHCP Discover (xid=715472D3)
                        0010C6E15021 *BROADCAST DHCP Discover (xid=715472D3)

                        I have no idea if the transaction ID and the xid should be the same,
                        so i will look into getting network monitor on my portable.
                        (not to keen on installing WireShark on the server)
                        Semper in faecibus sumus, sole profundum variat

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                        • #13
                          Re: DHCP not leasing in his own subnet

                          If you don't see any DHCP offer packets coming from the server then there's something wrong with the server (as opposed to the network). Are you using a filter for your capture? (make sure you capture traffic on ports 67 and 6
                          Last edited by JeremyW; 23rd May 2008, 15:32.
                          Regards,
                          Jeremy

                          Network Consultant/Engineer
                          Baltimore - Washington area and beyond
                          www.gma-cpa.com

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                          • #14
                            Re: DHCP not leasing in his own subnet

                            On the client i didn't apply a filter, on the server only filtered for the DHCP protocol...

                            And I can see other DHCP info from/for other DHCP clients in other scopes....
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                            • #15
                              Re: DHCP not leasing in his own subnet

                              OK, did you check the bindings and the firewall?
                              Regards,
                              Jeremy

                              Network Consultant/Engineer
                              Baltimore - Washington area and beyond
                              www.gma-cpa.com

                              Comment

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