Cluster support for DHCP servers
Updated: January 21, 2005
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
Cluster support for DHCP servers
The Windows Server 2003 DHCP Server service is a cluster-aware application. You can implement additional DHCP (or MADCAP) server reliability by deploying a DHCP server cluster using the Cluster service provided with Windows Server 2003, Enterprise Edition.
By using clustering support for DHCP, you can implement a local method of DHCP server failover, achieving greater fault tolerance. You can also enhance fault tolerance by combining DHCP server clustering with a remote failover configuration, such as by using a split scope configuration.
Requirements for setting up a DHCP clustered resource
The DHCP Server service, when used in a server cluster, requires the following resource types: a disk resource, an IP address resource, and a name resource.
In this type of configuration, a virtual IP address is defined for the IP address resource using the Cluster Administrator tool. This address must be a static IP address, not one obtained from another DHCP server.
The DHCP Server service then binds to this virtual IP address. This IP address must then be used to authorize the DHCP Server service in Active Directory so it can function correctly and service clients on the network.
Once the virtual IP is set using cluster configuration, each network adapter installed on each node (that is, a server in the cluster) needs an IP address configuration. Because the DHCP Server service does not bind to adapter IP addresses, you can either provide them through DHCP or configure them statically. If you use static configuration, the IP addresses for each linked pair of network adapters (linked node-to-node) should be from the same subnet.
Addresses that are statically configured using TCP/IP properties from the Network Connections folder can also be viewed through server bindings properties in the DHCP console. However, for a DHCP server cluster, the bindings information that appears in these views does not correspond to the virtual IP address used for the server cluster. Therefore, these settings do not apply.
When a scope is created for a DHCP clustered server, the virtual IP addresses used in the cluster context must be excluded so that they are not distributed to clients. Additionally. you should configure the database path, audit log file path, and the database backup path using the Cluster Administrator tool on the shared disk.
Other options for DHCP failover
Another way to implement DHCP remote failover is to deploy two DHCP servers in the same network that share a split scope configuration based on the 80/20 rule. For more information, see the section " Using the 80/20 rule for scopes" in Configuring scopes.
For more information about installing a DHCP resource type on a Windows Server 2003, Enterprise Edition, cluster server, see Checklist: Installing a DHCP Service resource.
The Jet database upon which the DHCP Server service relies is not cluster aware. If the clustered DHCP database becomes inaccessible to the DHCP Server service, the service will report thousands of ESENT application log errors, and DHCP service by the cluster will be interrupted.
If you need only to remotely manage DHCP server clusters that are deployed on remote computers running Windows Server 2003, Enterprise Edition, you can use Cluster Administrator to do this.
For more information about configuring DHCP clustering, see "Dynamic Host Configuration Protocol" at the Microsoft Windows Resource Kits Web site.