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  • Problem with DHCP

    Hi,

    I have a mysterious problem with DHCP-server in our network. Some random clients (Windows XP workstations) cannot obtain IP from DHCP-server (W2K3 Server). Sometimes they get IP without problems, sometimes it takes random time in minutes till they get IP and sometimes they cannot obtain IP at all. This problem occured suddenly. When i look to the DHCP-server, i can see the leases of those clients and evertyhing seems to be ok from server side.

    I rebooted DHCP-server but it didn't help. I looked DHCP-server logs and find nothing usefull.

    Ideas?

  • #2
    Re: Problem with DHCP

    Hi,

    Is there anything logged on the events on the client machines?
    Caesar's cipher - 3

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    • #3
      Re: Problem with DHCP

      Originally posted by Justin Credible View Post
      I rebooted DHCP-server but it didn't help. I looked DHCP-server logs and find nothing usefull. Ideas?
      Can you reproduce the problem by running ipconfig /release & ipconfig /renew commands? If you can, use Wireshark or Network Monitor to check whether DHCP traffic has any anomalies.

      How long are your DHCP lease times? Are there enough free addresses in your address pool?

      -vP

      Comment


      • #4
        Re: Problem with DHCP

        Originally posted by vonPryz View Post
        Can you reproduce the problem by running ipconfig /release & ipconfig /renew commands? If you can, use Wireshark or Network Monitor to check whether DHCP traffic has any anomalies.

        How long are your DHCP lease times? Are there enough free addresses in your address pool?

        -vP
        Randomly ipconfig /release & ipconfig /renew fixes the problem. DHCP lease time is 8 days. Address pool is not the problem, there are plenty of free adresses. I will try WireShark next to see what the DHCP traffic looks...

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        • #5
          Re: Problem with DHCP

          Originally posted by L4ndy View Post
          Hi,

          Is there anything logged on the events on the client machines?
          Need to check that.

          Comment


          • #6
            Re: Problem with DHCP

            This was found logged in client machine events: "The IP address lease 0.0.0.0 for the Network Card with network address *********** has been denied by the DHCP server 0.0.0.0 (The DHCP Server sent a DHCPNACK message)."

            What is that DHCP Server 0.0.0.0?

            When i looked DHCP server log i found machines that have problems obtaining ip from server, are renewing leases repeatedly.


            When i monitored network with WireShark, i can see DHCP NAK messages coming from address 0.0.0.0 and going to broadcast address 255.255.255.255 sometimes.
            Last edited by Justin Credible; 21st November 2008, 09:44.

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            • #7
              Re: Problem with DHCP

              Read through this monster Experts-Exchange thread. Keep scrolling all the way down to see if you can view the comments. If not, you can sign up for a truly free (I.e., it doesn't expire in 7 days) Ex-Ex account at this link. I don't want to simply copy and paste what the original posters said. This thread has a lot of different suggestions that might help you track the problem down. Ultimately, the problem was a setting on the DHCP server itseld. NOTE: All the way at the bottom, in the comments section, the author posts back what the problem was. I don't know if I'd get in trouble for copying the post here, so you'll just have to go see for yourself.

              Keep us up to date with what happens!
              Last edited by Nonapeptide; 21st November 2008, 18:43.
              Wesley David
              LinkedIn | Careers 2.0
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              • #8
                Re: Problem with DHCP

                Originally posted by Nonapeptide View Post
                Read through this monster Experts-Exchange thread. Keep scrolling all the way down to see if you can view the comments. If not, you can sign up for a truly free (I.e., it doesn't expire in 7 days) Ex-Ex account at this link. I don't want to simply copy and paste what the original posters said. This thread has a lot of different suggestions that might help you track the problem down. Ultimately, the problem was a setting on the DHCP server itseld. NOTE: All the way at the bottom, in the comments section, the author posts back what the problem was. I don't know if I'd get in trouble for copying the post here, so you'll just have to go see for yourself.

                Keep us up to date with what happens!
                I have no account to experts-exchange.. When i try to create new trial account, it asks creditcard number etc.

                I monitored network with WireShark and found something that might be causing these problems. When sending DHCPDISCOVER to network, randomly there are DHCP NAK message coming from ip 0.0.0.0 and going to broadcast address. I can see the sender MAC address and need to trace the owner now..
                Last edited by Justin Credible; 22nd November 2008, 10:36.

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                • #9
                  Re: Problem with DHCP

                  Originally posted by Justin Credible View Post
                  I have no account to experts-exchange.. When i try to create new trial account, it asks creditcard number etc.
                  Use the Firefox User Agent Switcher plugin and impersonate Googlebot to see all the answers on EE. Or Google the thread topic, go through Google referral link and scroll all the way down the fake footer to see the answers.

                  Anyway, check that your DHCP server doesn't have an address lease already given to the client MAC address.

                  Originally posted by Justin Credible View Post
                  there are DHCP NAK message coming from ip 0.0.0.0 and going to broadcast address. I can see the sender MAC address and need to trace the owner now..
                  I wonder if some of your clients are using static IP addresses overlapping the DHCP pool.

                  -vP

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                  • #10
                    Re: Problem with DHCP

                    For troubleshooting client side DHCP issues have a look at this for more info: - http://technet.microsoft.com/en-us/l.../cc757164.aspx

                    DHCP server 0.0.0.0 is telling you that the client might not be able to contact the DHCP server.
                    That can indicate there might be a communication fault between the two nodes.
                    Also make sure there is no other rogue DHCP servers in the network so these events are not generated from them.
                    Also I'd suggest you carefully examine the DHCP logs as any IP overlapping issues will be logged there.

                    @VonpryZ
                    Nice tip off regarding the EE. I was wondering why sometimes I could see the answers at the bottom and other times I couldn't access the same page.

                    Ta
                    Caesar's cipher - 3

                    ZKHQ BRX HYHQWXDOOB GHFLSKHU WKLV BRX ZLOO UHDOLVH LW ZDV D ZDVWH RI WLPH!

                    SFX JNRS FC U6 MNGR

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                    • #11
                      Re: Problem with DHCP

                      Originally posted by Justin Credible View Post
                      I have no account to experts-exchange.. When i try to create new trial account, it asks creditcard number etc.
                      When you click on the link I provided (this one) did you scroll down and click on the button that says "Become an Expert"?


                      Originally posted by Justin Credible View Post
                      I monitored network with WireShark and found something that might be causing these problems. When sending DHCPDISCOVER to network, randomly there are DHCP NAK message coming from ip 0.0.0.0 and going to broadcast address. I can see the sender MAC address and need to trace the owner now..
                      You could use Dhcploc.exe from "the Windows Support Tools found in the \Support\Tools folder on your Windows XP product CD" (quote taken from this link). That tool helps locate the presence of a rogue DHCP server on the network.

                      Do you have managed switches that will allow you to search for a MAC address in the ARP tables and trace it to a specific port?


                      Originally posted by L4ndy View Post
                      DHCP server 0.0.0.0 is telling you that the client might not be able to contact the DHCP server.
                      That can indicate there might be a communication fault between the two nodes.
                      Ultimately, I think that was the conclusion that the thread at Experts-Exchange came to. @Justin Credible: Maybe uninstall and reinstall the DHCP server portion? Just back up the DHCP information first.
                      Last edited by Nonapeptide; 22nd November 2008, 17:10.
                      Wesley David
                      LinkedIn | Careers 2.0
                      -------------------------------
                      Microsoft Certifications: MCSE 2003 | MCSA:Messaging 2003 | MCITP:EA, SA, EST | MCTS: a'plenty | MCDST
                      Vendor Neutral Certifications: CWNA
                      Blog: www.TheNubbyAdmin.com || Twitter: @Nonapeptide || GTalk, Reader and Google+: [email protected] || Skype: Wesley.Nonapeptide
                      Goofy kitten avatar photo from Troy Snow: flickr.com/photos/troysnow/

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                      • #12
                        Re: Problem with DHCP

                        Originally posted by Nonapeptide View Post
                        You could use Dhcploc.exe from "the Windows Support Tools found in the \Support\Tools folder on your Windows XP product CD" (quote taken from this link). That tool helps locate the presence of a rogue DHCP server on the network.


                        Ultimately, I think that was the conclusion that the thread at Experts-Exchange came to. @Justin Credible: Maybe uninstall and reinstall the DHCP server portion? Just back up the DHCP information first.

                        I use a gui tool called dhcpexplorer.exe findable on google.

                        I was gonna also suggest running these commands in a batch file or something on the client.

                        arp -d *
                        nbtstat -R
                        ipconfig /flushdns
                        nbtstat -RR
                        ipconfig /registerdns
                        ipconfig /release
                        ipconfig /renew

                        Another idea would be to install the dhcp server service on another server, then unauthorise, or stop the service/uninstall the other that's causing u hassle.
                        Please remember to award reputation points if you have received good advice.
                        I do tend to think 'outside the box' so others may not always share the same views.

                        MCITP -W7,
                        MCSA+Messaging, CCENT, ICND2 slowly getting around to.

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                        • #13
                          Re: Problem with DHCP (solved)

                          Problem solved!

                          MAC traced to WLAN AP. This WLAN AP caused these DHCP problems. Need to examine now why this happened... I will keep you informed! Thanks to all you people for helping me with this issue!

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