Network Load Balancing Manager (Nlbmgr.exe) is a new tool for Windows Server 2003. It provides the graphical interface for managing, monitoring, and configuring Network Load Balancing clusters. Its command-line counterpart is Nlb.exe. Both tools use the NLB application programming interface (API) to manage Network Load Balancing.
You create Network Load Balancing clusters using the Network Load Balancing Manager (see Figure 18-4). Start Network Load Balancing Manager from the Administrative Tools menu or by typing nlbmgr at the command prompt.
Figure 18-4. Use Network Load Balancing Manager to create and manage Network Load Balancing clusters
Once you've started Network Load Balancing Manager, you can create the new Network Load Balancing cluster by following these steps:
Right-click Network Load Balancing Clusters in the left pane, and then choose New Cluster. This displays the Cluster Parameters Wizard, as shown in Figure 18-5.
In the IP Address field, type the virtual IP address for the cluster. The IP address you assign is used to address the cluster as a whole and should be the IP address that maps to the full Internet name of the cluster that you provide in the Full Internet Name field.
In the Subnet Mask field, type the subnet mask for the cluster or accept the default. In most cases, if you aren't using subnetting, the default subnet mask value is what you should use. Check with your organization's network administrator if you are unsure.
In the Full Internet Name field, type the fully qualified domain name for the cluster, such as cluster.cpandl.com. This is the domain name by which the cluster will be known.
Next, set the Cluster Operations Mode as either Unicast or Multicast. By selecting Multicast, you can also enable IGMP Multicast. However, the multicast IP address is then restricted to the standard Class D address range (224.0.0.0 to 239.255.255.255).
Tip
Limit switch flooding
If the cluster hosts are directly connected to a hub and Internet Group Membership Protocol (IGMP) support is not enabled, incoming client traffic is automatically sent to all switch ports and can produce switch flooding. By enabling IGMP support for multicast clusters, you can limit switch flooding.
Note
Keep in mind that if you are working from a computer that has a single network adapter and that computer uses Network Load Balancing in unicast mode, you cannot use Network Load Balancing Manager on this computer to configure and manage other hosts. A computer with a single network adapter operating in unicast mode cannot communicate with other hosts in the cluster. You can, however, communicate with computers outside the cluster.
Optionally, you can enable Remote Control to allow the cluster to be managed remotely from another computer running the Windows operating system. Select Allow Remote Control, and then type and confirm the remote control password.
Caution
Allowing remote control of a Network Load Balancing cluster presents serious security risks, and before you do this, you should consider the consequences carefully. The security risks include the possibility of data tampering, denial of service, and disclosure of cluster traffic. If you decide to enable remote control, you should use a strong password that follows the strict security rules for user passwords in Windows domains.
Click Next. If the cluster will have additional virtual IP addresses, click Add, enter the virtual IP address and subnet mask information, then click OK. Repeat this process for each additional virtual IP address, and then click Next.
Using the Port Rules page, as shown in Figure 18-6, you can specify how the network traffic on a port is filtered. When you've configured multiple IP addresses for the cluster, you might want to configure filtering on a per–IP address basis. By default all TCP and UPD traffic directed to any cluster IP address that arrives on ports 0 to 65535 is balanced across all members of the cluster based on the load weight of each cluster member.
Click Next. Enter the domain name or IP address of the first host that will be a member of the cluster. Click Connect to connect to the server and display a list of available network interfaces. Select the network adapter that you want to use for Network Load Balancing, and then click Next. The IP address configured on this network adapter will be the dedicated IP address for this host and will be used for the public traffic of the cluster (as opposed to the private, node-to-node traffic).
On the Host Parameters page, shown in Figure 18-7, set the priority for this host in the cluster and the dedicated IP address that will be used to connect to this specific server. Afterward, set the initial state of this host when the Windows operating system is started. In most cases with deployed systems, you want the default state to be set as Started.
Note
The host priority is a unique host identifier that indicates the order in which traffic is routed among members of the cluster, and it ranges from 1 to 32. The host with ID 1 is the first to receive traffic, the host with ID 2 is the second, and so on. The dedicated IP address for the host is used for private node-to-node traffic (as opposed to the public traffic for the cluster). Again, it must be a fixed IP address and not a DHCP address.
Click Finish to start the Network Load Balancing service and configure the cluster using the specific initial host. You can then add hosts into the cluster as appropriate. If you need to change the cluster parameters later, right-click the cluster in the left pane, and select Cluster Properties. You are then able to change the cluster IP configuration, operation mode, and port rules.
Once you've created a cluster and added an initial host, at any time you can add other nodes to the cluster, up to a maximum of 32. Additional hosts automatically inherit the cluster port rules from the initial host. As mentioned previously, if you are working from a computer that has a single network adapter and that computer uses Network Load Balancing in unicast mode, you cannot use Network Load Balancing Manager on this computer to configure and manage other hosts.
To add a node to a Network Load Balancing cluster, follow these steps:
Start Network Load Balancing Manager from the Administrative Tools menu or by typing nlbmgr at the command prompt. If the cluster you want to work with isn't shown in the Network Load Balancing Manager, you can connect to it by right-clicking Network Load Balancing Clusters in the left pane and selecting Connect To Existing. On the Connect page, enter the domain name or IP address of any host in the cluster, and then click Connect. Select the cluster name to work with, and then click Finish.
In the left pane right-click the cluster to which you want to add a node, and select Add Host To Cluster. Enter the domain name or IP address of the host to add to the cluster. Click Connect to connect to the server and display a list of available network interfaces. Select the network adapter that you want to use for Network Load Balancing, as shown in Figure 18-8. The IP address configured on this network adapter will be the dedicated IP address for this host and will be used for the public traffic of the cluster (as opposed to the private, node-to-node traffic).
Click Next to display the Host Parameters page. Set the unique priority for this host in the cluster and the dedicated IP address that will be used to connect to this specific server. Afterward, set the initial state of this host when the Windows operating system is started. In most cases with deployed systems, you want the default state to be set as Started.
Click Finish to add the host to the cluster. When the host is added to the cluster, the cluster status changes to Converged temporarily while Network Load Balancing updates the cluster configuration. If you must change the host parameters later, rightclick the host in the left pane, and select Host Properties. You are then able to change the host priority, IP configuration, and initial state.
Network Load Balancing Manager provides several techniques for temporarily removing a node from a cluster, including the capability to suspend and resume load balancing on a pernode basis. If you no longer want a node to be a member of a Network Load Balancing cluster, you can remove it permanently from the cluster as well. To do this, start Network Load Balancing Manager from the Administrative Tools menu or by typing nlbmgr at the command prompt. Right-click the node in the left pane to remove it, and then select Delete Host. When prompted to confirm the action, click Yes.
Note
If the cluster you want to work with isn't shown in the Network Load Balancing Manager, you can connect to it by right-clicking Network Load Balancing Clusters in the left pane and selecting Connect To Existing. In the Connect dialog box, enter the domain name or IP address of any host in the cluster, and click Connect. Select the cluster name to work with, and then click Finish.
Events related to the Network Load Balancing service (the Windows Load Balancing Service, or WLBS) are stored in the System logs and can be accessed in Event Viewer. You can also enable logging related to the use of Network Load Balancing Manager. These events show the operations being performed in Network Load Balancing Manager.
To enable Network Load Balancing Manager logging, click Log Settings on the Options menu, check Enable Logging, and specify the full file path to the file you want to use for logging. Because this file contains sensitive information regarding the cluster, it should be stored in a secure folder accessible only to administrators.
Network Load Balancing Manager allows you to control operations on the cluster as a whole as well as for individual hosts within the cluster. You control cluster operations by right-clicking the cluster in the left pane of Network Load Balancing Manager, pointing to Control Hosts, and then selecting one of the following options:
Stop Stops all Network Load Balancing cluster traffic. Cluster operations are immediately stopped, and all existing connections are immediately closed.
Drainstop Disables all new traffic to the cluster but allows hosts to continue servicing active connections.
Suspend Stops all Network Load Balancing cluster traffic and also suspends clustercontrol commands, including remote control, except for resume and query. Cluster operations are immediately stopped, and all existing connections are immediately closed.
Resume Reenables the use of cluster-control commands for the cluster, including remote control. This option doesn't restart cluster operations, however.
Start Starts or restarts the handling of Network Load Balancing traffic for the cluster.
You can manage the Cluster service on a specific host by right-clicking the host, pointing to Control Host, and then selecting one of the following options:
Stop Stops Network Load Balancing on the host, and all existing connections to the host are immediately closed.
Drainstop Disables all new traffic to the host but allows the host to continue servicing any active connections.
Suspend Stops all Network Load Balancing on the host and also suspends clustercontrol commands, including remote control, except for resume and query.
Resume Reenables the use of cluster-control commands for the host, including remote control. This option doesn't restart cluster operations, however.
Start Starts or restarts the handling of Network Load Balancing traffic for the host.