After DHCP is properly configured on one server in your cluster, you must create and configure a DHCP resource in Novell Cluster Services. This includes configuring DHCP load and unload scripts, setting DHCP Failover and Failback modes, and assigning the DHCP resource to specific servers in your cluster.
Novell Cluster Services includes a DHCP resource template, which greatly simplifies the process for creating a DHCP cluster resource. Much of the DHCP cluster resource configuration is performed automatically by the DHCP resource template.
To create a cluster resource:
In ConsoleOne®, browse to and select the Cluster object.
Click File > New > Cluster > Cluster Resource.
Enter a name for the DHCP cluster resource.
Enter the DHCP template name in the Inherit from Template field, or browse and select it from the list.
Check the Define Additional Properties check box, click Create, and then continue with Editing DHCP Load and Unload Scripts.
The DHCP resource template configures the DHCP resource by automatically creating DHCP load and unload scripts, setting failover and failback modes, and assigning DHCP as a resource to all nodes in the cluster.
The DHCP resource template automatically creates a load and unload script to start and stop the DHCP service on servers in your cluster. The load script contains commands that you must customize for your specific DHCP configuration.
To edit the DHCP load script:
In ConsoleOne, right-click the DHCP Resource object and then click Properties.
If you just created the DHCP resource object and checked the Define Additional Properties check box, the DHCP Resource object should already be displayed.
Click the Scripts tab on the property page and select Cluster Resource Load Script.
The load script will appear similar to the following example:
CLUSTER DHCP CN=SERVER.O=ORG.T=TREE dhcpsrvr --servaddr=A.B.C.D
The CLUSTER DHCP command is necessary to pass DHCP-specific configuration information to another server in the cluster if the server where DHCP is running fails.
The DHCPSRVR command and command switches are used to start the DHCP server (dhcpsrvr.nlm) on a NetWare server.
Edit the CLUSTER DHCP command to add the context of the Server object for the server in your cluster that has DHCP configured.
For example, if the server context is CN=PROD1.O=SALES.T=ACME_TREE, the line in the load script would appear as follows:
CLUSTER DHCP CN=PROD1.O=SALES.T=ACME_TREE
The server context specified in the load script does not change even though the load script will run on another server in the cluster during a failover.
Edit the DHCPSRVR command to assign a unique IP address to the DHCP cluster resource.
For example, if the unique IP address for the DHCP cluster resource is 10.10.153.10, the line in the load script would appear as follows:
dhcp --servaddr=10.10.153.10
The IP address for the DHCP cluster resource allows clients to reconnect to that address regardless of which server is hosting it.
Click the Unload Script tab on the property page to view the unload script.
The UNLOAD DHCPSRVR command is by default the only command in the unload script.
The DHCP resource template sets the DHCP resource Start Mode and Failover Mode to AUTO, and the Failback Mode to DISABLE.
If the DHCP resource Start Mode is set to AUTO, the DHCP server automatically loads on a designated server when the cluster is first brought up. If the DHCP Start Mode is set to MANUAL, you can manually start DHCP on a specific server when you want, instead of having it automatically start when servers in the cluster are brought up.
If the DHCP Failover Mode is set to AUTO, the DHCP server automatically moves to the next server in the Assigned Nodes list in the event of a hardware or software failure. If the DHCP Failover Mode is set to Manual, you can intervene after a failure occurs and before the DHCP server is started on another node.
If the DHCP Failback Mode is set to DISABLE, the DHCP server will continue running on the node it has failed to. If the DHCP Failback Mode is set to AUTO, the DHCP server automatically moves back to its preferred node when the preferred node is brought back online. Set the DHCP Failback Mode to MANUAL to prevent the DHCP server from moving back to its preferred node when that node is brought back online, until you are ready to allow it to happen.
To view or change DHCP Start, Failover, and Failback modes, do the following:
In ConsoleOne, right click the DHCP Resource object and select Properties.
Click the Policies tab on the property page.
View or change the Start, Failover, or Failback modes for DHCP.
The DHCP resource template automatically assigns the DHCP resource to all nodes in the cluster. The order of assignment is the order the nodes appear in the resource list. To view or edit DHCP resource node assignments or change the server failover order:
In ConsoleOne, right-click the DHCP Resource object and select Properties.
Click the Nodes tab on the property page.
View the current DHCP resource server assignments and, if necessary, click the right or left arrow button to assign or unassign servers to the DHCP resource.
You can also click the up or down arrow button to change the failover order of the servers assigned to DHCP.
If you have DHCP clients that are located on a separate LAN segment or IP subnet from the servers in your cluster, some additional configuration is necessary. This additional configuration consists of adding and deleting a secondary IP address on the cluster server where DHCP is running and setting up your router to forward DHCP requests.
To add a secondary IP address:
Edit the DHCP cluster resource load script and add the following line:
ADD SECONDARY IP ADDRESS A.B.C.D
Replace A.B.C.D with a unique IP address. Your router will forward DHCP requests from other LAN segments to this address.
Edit the DHCP cluster resource unload script and add the following line:
DEL SECONDARY IP ADDRESS A.B.C.D
Replace A.B.C.D with the same IP address you added in the load script.
To configure a router to forward DHCP requests, see your router documentation. If you are using a NetWare server as a router, ensure the following line is added to the autoexec.ncf file of the server acting as a router:
BOOTPFWD SERVER=A.B.C.D
Replace A.B.C.D with the secondary IP address you specified in the load and unload scripts above.
For additional information on setting up and configuring Novell Cluster Services, See the NW6.5 SP8: Novell Cluster Services 1.8.5 Administration Guide.