Network Load Balancing Tools and Settings

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

In this section

• Network Load Balancing Tools

• Network Load Balancing Registry Entries

• Network Load Balancing WMI Classes

• Network Port Used by Network Load Balancing

This section provides summary information about the tools, registry entries, WMI classes, and network ports associated with Network Load Balancing. This information is helpful when evaluating Network Load Balancing to determine what tools are available to assist in deployment and operations tasks.

Network Load Balancing Tools

The following tools are associated with Network Load Balancing.

NLB.exe command: Network Load Balancing control program

Category

Tool included in the Windows Server 2003 family, Windows 2000 Standard Server SP 3 and later, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

Version compatibility

Available on computers running the Windows Server 2003 family of products, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

The Nlb.exe command replaces Wlbs.exe. Windows NT Load Balancing Service (WLBS) is the former name of Network Load Balancing in Windows NT Server 4.0. For reasons of backward compatibility, WLBS continues to be used in certain instances.

You can perform most cluster operations by using the nlb.exe command. Nlb.exe performs the following functions:

• Suspend and resume all cluster operations. The reason you would suspend operations is to override any remote control commands that might be issued. Resuming cluster operations would not restart the operations, but would enable use of cluster-control commands, including remote control commands.

• Start and stop cluster operations on the specified hosts.

• Disable all new traffic handling on the specified hosts.

• Enable and disable traffic handling for the rule whose port range contains the specified port.

• Display the current cluster state and the list of host priorities for the current members of the cluster.

• Display information about a given port rule.

• Reload the Network Load Balancing driver’s current parameters from the registry.

• Display extensive information about the current Network Load Balancing parameters, cluster state, and past cluster activity. The last several event log records produced by Network Load Balancing are shown, including the binary data attached to those records. This assists in technical support and debugging.

• Display information about the current Network Load Balancing configuration.

• Display the media access control (MAC) address corresponding to the specified cluster name or IP address.

Nlbmgr.exe: Network Load Balancing Manager

Category

Tool included in the Windows Server 2003 family.

Version compatibility

Available on computers running the Windows Server 2003 family of products, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server. This tool is also part of the Windows Server 2003 Administration Tools Pack, which you can install on computers running Windows XP Professional. You can use Network Load Balancing Manager on Windows XP Professional only to manage Network Load Balancing clusters on remote computers running the Windows Server 2003 family of products. You cannot install the Network Load Balancing service itself on Windows XP Professional.

Network Load Balancing Manager is used to create and manage Network Load Balancing clusters and all cluster hosts from a single computer, and you can also replicate the cluster configuration to other hosts. By centralizing administration tasks, Network Load Balancing Manager helps eliminate many common configuration errors.

Network Load Balancing Registry Entries

The following registry entries are associated with Network Load Balancing.

The information here is provided as a reference for use in troubleshooting or verifying that the required settings are applied. It is recommended that you do not directly edit the registry unless there is no other alternative. Modifications to the registry are not validated by the registry editor or by Windows before they are applied, and as a result, incorrect values can be stored. This can result in unrecoverable errors in the system. When possible, use Group Policy or other Windows tools, such as Microsoft Management Console (MMC), to accomplish tasks rather than editing the registry directly. If you must edit the registry, use extreme caution.

For more information about the following registry entries, see the Registry Reference in Tools and Settings Collection.

network adapter ID subkey

The following registry entries are located under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters\Interface\network adapter ID subkey.

AliveMsgPeriod

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters\Interface\network adapter ID subkey

Version

Available in the Windows Server 2003 family, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

Modifying this registry entry allows you to control both the message exchange period and the number of missed messages required to initiate convergence. Modifying the AliveMsgTolerance registry entry will also allow you to do this. The AliveMsgPeriod value holds the message exchange period in milliseconds, and the AliveMsgTolerance value specifies how many exchanged messages from a host can be missed before the cluster initiates convergence.

The values you enter should reflect your installation’s requirements. A longer message exchange period reduces the heartbeat traffic needed to maintain fault tolerance, but it increases the time that it takes for Network Load Balancing to stop sending network messages to an offline host. Likewise, increasing the number of message exchanges prior to convergence reduces the number of unnecessary convergence initiations due to network congestion, but it too increases the time for an offline host to stop receiving network traffic.

Using the default values, 5 seconds are needed to discover a missing host, and another 5 seconds are needed for the cluster to redistribute the load. A total of 10 seconds to stop sending network traffic to an offline host should be acceptable for most TCP/IP applications. This configuration incurs very low networking overhead.

Default value: 1000 (1 second)

Possible range: 100–10000

AliveMsgTolerance

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters\Interface\network adapter ID subkey

Version

Available in the Windows Server 2003 family, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

Modifying this registry entry allows you to control both the message exchange period and the number of missed messages required to initiate convergence. Modifying the AliveMsgPeriod registry entry will also allow you to do this. For more information, see the previous description for AliveMsgPeriod.

Default value: 5

Possible range: 5–100

DescriptorsPerAlloc

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters\Interface\network adapter ID subkey

Version

Available in the Windows Server 2003 family, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

Determines the number of connection descriptors allocated at a time. Connection descriptors are used to track TCP connections.

Default value: 512

Possible range: 16–1024

MaskSourceMAC

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters\Interface\network adapter ID subkey

Version

Available in the Windows Server 2003 family, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

Enables masking of the media access control (MAC) address. The MAC address is used for communication between network adapters on the same subnet. Each network adapter has an associated MAC address.

If the host is connected to a switch when Network Load Balancing is running in unicast mode, set the value of MaskSourceMAC to 1 (the default). If the Network Load Balancing host is running in unicast mode and is attached to a hub that is then connected to a switch, set the value of this entry to 0. If Network Load Balancing is running in multicast mode, this setting has no effect.

Default value: 1

Possible range: 0–1

MaxDescriptorAllocs

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters\Interface\network adapter ID subkey

Version

Available in the Windows Server 2003 family, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

Determines the maximum number of times the connection descriptors can be allocated. This value limits the maximum memory footprint of Network Load Balancing.

Default value: 512

Possible range: 1–1024

NetmonAliveMsgs

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters\Interface\network adapter ID subkey

Version

Available in the Windows Server 2003 family, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

Determines whether Network Monitor (NetMon) captures Network Load Balancing heartbeat messages on the local host.

To allow NetMon to capture Network Load Balancing heartbeat messages on the local host, set the value of this entry to 1. To get the best performance, leave the value of this entry at its default value of 0.

NumActions

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters\Interface\network adapter ID subkey

Version

Available in the Windows Server 2003 family, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

This key is an internal Network Load Balancing entry. Increase the value of this entry only if you encounter an event log message that advises you to do so.

Default value: 100

Possible range: 5–500

NumAliveMsgs

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters\Interface\network adapter ID subkey

Version

Available in the Windows Server 2003 family, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

This is an internal Network Load Balancing entry. Increase the value of this entry only if you encounter an event log message that advises you to do so.

Default value: 66

Possible range: 5–500

NumPackets

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters\Interface\network adapter ID subkey

Version

Available in the Windows Server 2003 family, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

This is an internal Network Load Balancing entry. Increase the value of this entry only if you encounter an event log message that advises you to do so.

Default value: 200

Possible range: 5–500

RemoteControlUDPPort

Registry path

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WLBS\Parameters\Interface\network adapter ID subkey

Version

Available in the Windows Server 2003 family, Windows 2000 Advanced Server, and Windows 2000 Datacenter Server.

Determines the UDP port that is used by Network Load Balancing to receive remote control messages. Note that for backwards compatibility, Network Load Balancing automatically listens to port 1717. If you decide to firewall the remote control port to block remote control messages, you also always need to firewall port 1717.

Do not use ports that are commonly used for other purposes (such as those used for FTP or DNS).

Default value: 2504

Note

• DecriptorsPerAlloc, MaxDescriptorAllocs, NumActions, NumPackets, and NumAliveMsgs only take effect when the Network Load Balancing driver is binding to the network adapter (upon restarting the hosts, or through disabling and then re-enabling the network adapter). The remaining settings will take effect when the Network Load Balancing driver binds to the network adapter, or when Network Load Balancing is reloaded (using Nlb.exe reload command).

Network Load Balancing WMI Classes

The following table lists and describes the WMI classes that are associated with Network Load Balancing.

WMI Classes Associated with Network Load Balancing

For more information about these WMI classes, see the WMI SDK documentation on MSDN.

Network Port Used by Network Load Balancing

Network Load Balancing uses the following network port.

Network Ports Used by Network Load Balancing

Port numbers in a range of 0 to 65,535 are currently supported by Network Load Balancing for TCP/UDP. The default port range is 0 to 65,535. To load-balance all client requests with a single port rule, use the default port range. By using the default port range, you do not have to worry about which port or ports are associated with the application whose client requests you are load-balancing.