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  • DHCP, not working properly?

    Hi,

    Here at work there are several PC's that get an ip. my scope is from 192.168.0.50-252, but some PC's get 192.168.1.x? Does anybody know the reason for this? My DNS server is a windows 2003 server, and I've never had similar problems.

    Everything else is correct. The DNS-suffix, netmask, gateway and DNS server all have the correct settings.

  • #2
    Re: DHCP, not working properly?

    some router or a other dhcp server who is leasing those addresses?
    Marcel
    Technical Consultant
    Netherlands
    http://www.phetios.com
    http://blog.nessus.nl

    MCITP(EA, SA), MCSA/E 2003:Security, CCNA, SNAF, DCUCI, CCSA/E/E+ (R60), VCP4/5, NCDA, NCIE - SAN, NCIE - BR, EMCPE
    "No matter how secure, there is always the human factor."

    "Enjoy life today, tomorrow may never come."
    "If you're going through hell, keep going. ~Winston Churchill"

    Comment


    • #3
      Re: DHCP, not working properly?

      Could some of the PC's have a static IP? We have some here for the banking needs to get through the firewall.

      Also, like Dumber said, is there another DHCP server on the network?

      Comment


      • #4
        Re: DHCP, not working properly?

        No, they dont have static ip. I havent set up any other dhcp servers either. Some time ago I had a router as the dhcp server, but that is dissabled now. I've also had some problems with people using VMware, they act as DHCP servers, but then I get dns-suffix: localhost, and a totally different ip. It seems like when the dhcp lease goes out, they get the 192.168.1.x. If I just ipconfig /release and then renew, it gets the right ip staight away.....

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        • #5
          Re: DHCP, not working properly?

          Do the affected PC's have these addresses setup in the alternate configuration sheets of the IP/TCP Properties? Possibly they have been unable to contact the DHCP server and have used these instead?
          A recent poll suggests that 6 out of 7 dwarfs are not happy

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          • #6
            Re: DHCP, not working properly?

            Go to a command prompt and type Netsh. In the Net Shell console type: dhcp show server. This command will show you all DHCP servers found in AD on your network.

            Comment


            • #7
              Re: DHCP, not working properly?

              I believe Netsh will only locate DHCP servers autorized in the network.

              Personally I would use Dhcploc.exe
              http://technet2.microsoft.com/window....mspx?mfr=true
              Or DHCP_Probe
              http://www.net.princeton.edu/software/dhcp_probe/

              Both utils will probe for any DHCP server in the network.
              Marcel
              Technical Consultant
              Netherlands
              http://www.phetios.com
              http://blog.nessus.nl

              MCITP(EA, SA), MCSA/E 2003:Security, CCNA, SNAF, DCUCI, CCSA/E/E+ (R60), VCP4/5, NCDA, NCIE - SAN, NCIE - BR, EMCPE
              "No matter how secure, there is always the human factor."

              "Enjoy life today, tomorrow may never come."
              "If you're going through hell, keep going. ~Winston Churchill"

              Comment


              • #8
                Re: DHCP, not working properly?

                Originally posted by Dumber View Post
                I believe Netsh will only locate DHCP servers autorized in the network.

                Personally I would use Dhcploc.exe
                http://technet2.microsoft.com/window....mspx?mfr=true
                Or DHCP_Probe
                http://www.net.princeton.edu/software/dhcp_probe/

                Both utils will probe for any DHCP server in the network.
                Correct. If the server is authorized it can distribute IP address`s. Although naturally there can only be 1 authoritative DHCP on a subnet. Im not familiar with the second link you have posted. Its a .tar file and can only be used on a linux distro. Presumably it does the same job as the windows support tools version?

                Comment


                • #9
                  Re: DHCP, not working properly?

                  Great, thanks allot for all the replies, I'll try this first thing tomorrow.

                  Comment


                  • #10
                    Re: DHCP, not working properly?

                    Originally posted by scurlaruntings View Post
                    Correct. If the server is authorized it can distribute IP address`s. Although naturally there can only be 1 authoritative DHCP on a subnet. Im not familiar with the second link you have posted. Its a .tar file and can only be used on a linux distro. Presumably it does the same job as the windows support tools version?
                    Yeah well... Routers can still give out DHCP addresses... Vmware still can lease DHCP addresses
                    The second one is indeed for linux. I'm a bit playing with linux so I forgot to mention it
                    Indeed it's has the same goal as the one from the support tools

                    Oh. you also can run an ipconfig /all on the client which has an incorrect ipaddress and see who is the DHCP server
                    Marcel
                    Technical Consultant
                    Netherlands
                    http://www.phetios.com
                    http://blog.nessus.nl

                    MCITP(EA, SA), MCSA/E 2003:Security, CCNA, SNAF, DCUCI, CCSA/E/E+ (R60), VCP4/5, NCDA, NCIE - SAN, NCIE - BR, EMCPE
                    "No matter how secure, there is always the human factor."

                    "Enjoy life today, tomorrow may never come."
                    "If you're going through hell, keep going. ~Winston Churchill"

                    Comment


                    • #11
                      Re: DHCP, not working properly?

                      Originally posted by Dumber View Post
                      Yeah well... Routers can still give out DHCP addresses... Vmware still can lease DHCP addresses
                      The second one is indeed for linux. I'm a bit playing with linux so I forgot to mention it
                      Indeed it's has the same goal as the one from the support tools

                      Oh. you also can run an ipconfig /all on the client which has an incorrect ipaddress and see who is the DHCP server
                      It will be interesting to know if theres a tool that can intercept DHCP packets on a given network and report any malicious DHCP activity much easier than Netsh and Dhcploc.exe. Netmon can probably do it but its quite granular..

                      Comment


                      • #12
                        Re: DHCP, not working properly?

                        what is the syntax to find the rouge dhcp server? (I just get errors)

                        Comment

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