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by Stefan Hellman | |||||||||||||||
| The version history | The DHCP Redundancy Forum | Download DHCP Redundancy | ||||||||||||||
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BACKGROUND | You may have clustered firewalls, redundant fileservers and daily backups but the DHCP server is often an underestimated part of the network. If the DHCP server goes down your clients cant acces your network.To cluster the service you need Windows Server 2003 Enterprise edition or some third party software. Those solutions are quite expensive. Thats why I started this DHCP-Redundancy project. We are currently running it at one of our networks with about 4500 client computers and it is working very good so far, soon we are installing it on our second network with about the same amount of clients. |
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THE TECHNIQUE | What I have done is to install the DHCP service on a second server wich every night replicates the settings, reservations and leases from the main DHCP server. On the router I added a second DHCP relay address pointing to the second DHCP server. The big thing is the redundancy service that I created and is installed on the second server. The service checks once a minute the status of the main DHCP server and starts or stops the second DHCP service based on the status of the main DHCP service. If the main service is down it starts the second and if the main comes up it stops the second, and since the router forwards the DHCP requests to both servers there is always one thats answering. If you only have reserverations for all the computers it works perfect, if you have open scopes it also works very well if you dont have to short lease times, at least 5 days but the longer the better. |
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INSTALLATION | .Net-framework v.2.0 or higher must be installed on the second server. NOTE! So far, DHCP-Redundancy only supports English, Polish, German and Swedish versions of 2003 Server. If you have another language and want to help the project, leave a message in the forum at the top of this page. If you are installing DHCP-Redundancy service for the first time, read the installation instructions. If you are upgrading to v1.22 from an older release, read the upgrading instructions. |
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TIPS & TRICKS | If your main server is down for a long period of time so that the database get outdated or you have to reinstall the service or the whole server, you can export the database from the second server and import it to your main server before you bring it back in service. On the second server use the command: netsh dhcp server export c:\temp\dhcp-export.txt all Then, on your main server use the command: netsh dhcp server import c:\temp\dhcp-export.txt all The DHCP-service has to be running when you import or exporting the database, and you have to delete any existing scope that will be imported on your main server If you change the settings with DHCP-Redundancy-config.exe you have to stop and start the DHCP-Redundancy service for the new settings take effect. |
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TROUBLESHOOTING | Under construction The service writes errormessages to the application log in the event viewer. |