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  • DHCP fall back on windows 2003

    Hi,

    I am having DHCP server with windows 2003 OS , Actually i need to configure two DHCP server with fall back option.is any way is there to configure DHCP server

  • #2
    Re: DHCP fall back on windows 2003

    Hi,

    You can choose between a Proactive approach by which you install the DHCP server in another 2003 box on the same subnet and setup two non overlaping scopes Something like a 50/50 or 80/20 rule.
    Otherwise you could go for a Reactive approach by which you create a stand by DHCP server configured the same as the first one but Not Activated.
    You then setup some sort of notification when the DHCP server service fails on the active DHCP server and activate the Second one until you troubleshoot the first.
    Caesar's cipher - 3

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    • #3
      Re: DHCP fall back on windows 2003

      its your organisation has around 100- 120 PC's

      then 50/50 option is the best as its a proactive and will works as backup to.

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      • #4
        Re: DHCP fall back on windows 2003

        HI L4ndy,

        As per your second commets standby DHCP but can you clarify how can we setup notification...if primary DHCP goes done...& how does it replicate data

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        • #5
          Re: DHCP fall back on windows 2003

          it will not do anything untill u manually activate it but this is manual process and only when your main server crash. You cannot have two server doing DHCP with the same scope at the same time. That will make thing more worst.

          to activate all u have to do is just right click and select activate on the DHCP option

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          • #6
            Re: DHCP fall back on windows 2003

            Originally posted by lisa804u View Post
            HI L4ndy,

            As per your second commets standby DHCP but can you clarify how can we setup notification...if primary DHCP goes done...& how does it replicate data

            On your DHCP server go to services.msc and look for a service called DHCP server (DHCPServer). Go to its properties and the recovery Tab.
            On the First failure select Run a Program.
            In the mean time you would have saved a file named let's say e-mail.vbs somewhere on the server.
            the Following file contents obviously will have to be altered to match your org:

            Code:
            Set objEmail = CreateObject("CDO.Message")
            
            objEmail.From = "[email protected]"
            objEmail.To = "[email protected]"
            objEmail.Subject = "Subject" 
            objEmail.Textbody = "Text body"
            objEmail.Configuration.Fields.Item _
                ("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2
            objEmail.Configuration.Fields.Item _
                ("http://schemas.microsoft.com/cdo/configuration/smtpserver") = _
                    "Your SMTP Server" 
            objEmail.Configuration.Fields.Item _
                ("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = 25
            objEmail.Configuration.Fields.Update
            objEmail.Send
            On the Run Program section, browse to the e-mail.vbs make sure Append fail count is selected as well.
            Ok when you're done.
            Give this a go and you'll get e-mail notification when the DHCP server stops.
            you won't get any alerts if there is a problem with the dhcp server and is not dashing out IP leases for some reason thus it is not a complete solution.

            If the first DHCP goes down, (The service stops to be more accurate) you'll get the e-mail notification and will authorise the second one which will start serving ip configuration straight away. No data need to be replicated or policies propagated, the way DHCP works is on a first come - first serve basis.
            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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            • #7
              Re: DHCP fall back on windows 2003

              Hi L4ndy,

              If i have two DHCP Server & manual Activation is required for second one.

              Let have one scenario,Suppose my first DHCP server goes down & i had manual activate my Second server with same scope.than on Client Workstation if
              some workstation renew it IP address than there is chance of 100 % probability of conflicting ip address.

              than as per your comment "No data need to be replicated or policies propagated,"

              Should not be fulfill this scenario.

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              • #8
                Re: DHCP fall back on windows 2003

                Incorrect, you have to reconfigure the DHCP to (for example)
                DHCP Server A deploys: 192.168.10.1 - 192.168.10.200
                DHCP Server B deploys: 192.168.10.201 - 192.168.10.254

                Or for example:
                For server A: 192.168.10.1 - 192.168.10.254 but exclude 192.168.10.100 - 192.168.10.150
                and for server B: 192.168.10.100 - 192.168.10.150 and exclude the rest.

                However there is more then this:
                check this out.
                http://www.windowsdevcenter.com/pub/...CP_Server.html
                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"

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                • #9
                  Re: DHCP fall back on windows 2003

                  Same scope configurations would also work but you need to enable IP address conflict detection on your DHCP servers and set it to 2, then each DHCP server will test an address three times to make sure it's not already being used before leasing it to a client, and this will prevent one server from leasing an address that the other server has already leased.
                  That could potentially make the initial IP assignment slower but it'll avoid any possible problems.
                  This is also mentioned in Dumbers link.
                  Or you could use the Netsh command to backup and restore the DHCP database and then Reconcile it.

                  So many ways to skin a cat
                  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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                  • #10
                    Re: DHCP fall back on windows 2003

                    Some more info here:

                    It will be tempting to build each DHCP server with half the scope but resist this. DHCP works by accepting whatever server responds first to the server location broadcast. If each has half of the DHCP range and it tries to renew with the wrong server, the workstation will get a NAK message. Unfortunately, the workstation may not always try again when it gets the NAK and will simply drop off the network. I like to call this NAK poisoning (though I am sure this is probably not my term)

                    To get around this, have both servers host the whole range and have reciprocal exclusions so if the renewal is out of range, the server will offer a substitute address rather than a NAK.

                    Example on a 192.168.1.0/24 network
                    Server 1: 192.168.1.0/24 range excludes 192.168.1.129-254
                    Server 2. 192.168.1.0/24 range excludes 192.168.1.1-128

                    Note that this is 50/50... Note that normal distribution is 80/20 here the 80 can handle the entire required number of hosts. Just remember if you're going to split the servers across a routed boundary to include an IP Helper-Address (on Cisco)command to allow foreign solicitations. The local one will almost always respond first unless it is down.
                    Last edited by ethos; 21st April 2009, 18:04.

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