Announcement

Collapse
No announcement yet.

DHCP duplicate leases

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • DHCP duplicate leases

    Hello,

    I have a Windows Server 2008 domain controller with DHCP installed, this server is called "exchange". I moved the DHCP services off a Windows Server 2003 a few weeks ago. It gives out DHCP to PC's and everything without an issue. One thing it does though for some strange reason is in the list of leases it keeps getting lots of entries for my "terminalserver" and the "exchange" server, both of which are set with static IP addresses! I dont have any reservations set for these servers but I have excluded their static IP's using the exclusions.
    Both of these servers are Virtual Machines running on VMWare platform, the main server called "exchange" has an E1000 virtual network card and the "terminalserver" has a VMXNET 3 virtual network card.

    I've checked for any duplicate DNS entries for these servers and there are no issues from what I can see.

    The problem it's causing is that there aren't many available IP's anyway so when these servers take about 8 each its robbing the only remaining addresses.
    To temporarily get around the problem I go into the list of DHCP leases and just delete all the entries for these two servers.

    Any ideas of a solution to permanently stop this happening?
    Thanks a lot
    Mark

  • #2
    Re: DHCP duplicate leases

    Do the servers host remote access solutions, or have they done so in the past? I see this when remote access servers grab a handful of addresses for VPN clients.
    A recent poll suggests that 6 out of 7 dwarfs are not happy

    Comment


    • #3
      Re: DHCP duplicate leases

      Hi thanks for your reply! The terminal server does have Routing and Remote access setup on it yes. However the server grabs way more IPs from DHCP than the amount of VPN connections that are being used. Also the exchange server never has had any remote access setup on it and it's a brand new virtual machine...

      Comment


      • #4
        Re: DHCP duplicate leases

        The routing and remote access role will generally grab between 8 and 10 regardless of how few connections are made. We only have 4 people using the VPN at any one time, but the server always has about 10 addresses available.

        I don't know how the Exchange server might function in this regard.

        What other roles/features/applications are installed? Perhaps one of those is grabbing the addresses.
        A recent poll suggests that 6 out of 7 dwarfs are not happy

        Comment


        • #5
          Re: DHCP duplicate leases

          Originally posted by markdavies View Post
          Hi thanks for your reply! The terminal server does have Routing and Remote access setup on it yes. However the server grabs way more IPs from DHCP than the amount of VPN connections that are being used. Also the exchange server never has had any remote access setup on it and it's a brand new virtual machine...
          configure less actual available VPN ports
          Please do show your appreciation to those who assist you by leaving Rep Point https://www.petri.com/forums/core/im.../icon_beer.gif

          Comment


          • #6
            Re: DHCP duplicate leases

            By default the VPN role will grab 10 addresses from DHCP. Once it's used the 10 it will grab 10 more.

            You can modify this behavior by editing the registry.

            More info: http://technet.microsoft.com/en-us/l.../cc958904.aspx
            Regards,
            Jeremy

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

            Comment


            • #7
              Re: DHCP duplicate leases

              1. DHCP shouldn't be on your exchange server, so hopefully it's not.
              2 scope what is your IP scope 10.10.10.xxx/24? (10.10 only example) if so that is 253 usable IP addresses.
              2. you can change your subnet to 10.10.10.xxx/22 and that will give over 1,000 usable IP addresses.

              Comment


              • #8
                Re: DHCP duplicate leases

                Originally posted by bigalusn View Post
                1. DHCP shouldn't be on your exchange server, so hopefully it's not.
                2 scope what is your IP scope 10.10.10.xxx/24? (10.10 only example) if so that is 253 usable IP addresses.
                2. you can change your subnet to 10.10.10.xxx/22 and that will give over 1,000 usable IP addresses.
                1. I haven't heard any issues with an Exchange server running DHCP. It's not recommended for Exchange to be on a DC but it is supported (like SBS and a single server setup)
                2. There's 254 usable in a /24... or were you subtracting one for the gateway?
                2. (3.?) I would not recommend making this change without understanding the specific network. You wouldn't want that many devices in the same broadcast domain. Not to mention the potential routing implications, possible use of public IPs, etc.
                Regards,
                Jeremy

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

                Comment


                • #9
                  Re: DHCP duplicate leases

                  The company I am having difficulty in dealing with issues dividing ip . IT companies are less frequent dropouts

                  Comment


                  • #10
                    Re: DHCP duplicate leases

                    Is this an answer to the original thread, or another question.

                    Either way, I'm afraid it makes absolutely no sense at all!
                    Tom Jones
                    MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
                    PhD, MSc, FIAP, MIITT
                    IT Trainer / Consultant
                    Ossian Ltd
                    Scotland

                    ** Remember to give credit where credit is due and leave reputation points where appropriate **

                    Comment

                    Working...
                    X