Microsoft KB Archive/812870

= Network Load Balancing cluster node does not successfully converge =

Article ID: 812870

Article Last Modified on 10/30/2006

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APPLIES TO


 * Microsoft Windows 2000 Advanced Server

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SYMPTOMS
When you run the WLBS display command or the WLBS query command on a Network Load Balancing cluster host, you receive results that indicate that the cluster host is not converging successfully, or that the cluster is converging only with itself. For example, you may receive results that are similar to one of the following:  Returned results that indicate that the cluster hosts are converging, but that convergence does not complete:

WLBS Cluster Control Utility V2.4 (c) 1997-2003 Microsoft Corporation. Cluster 192.168.192.4 Host 2 has entered has entered a converging state 1 time(s) since joining the cluster and is still in a state of convergence. Host 2 converging with the following host(s) as part of the cluster: 1

WLBS Cluster Control Utility V2.4 (c) 1997-2003 Microsoft Corporation. Cluster 192.168.192.4 Host 2 has entered has entered a converging state 1 time(s) since joining the cluster and is still in a state of convergence. Host 2 converging with the following host(s) as part of the cluster:

Note In this second example, no host number appears after the colon in the returned results.

 Returned results that indicate that the cluster hosts are converging with themselves only:

WLBS Cluster Control Utility V2.4 (c) 1997-2003 Microsoft Corporation. Cluster 192.168.192.4 Host 2 has entered has entered a converging state 1 time(s) since joining the cluster and is still in a state of convergence. Host 2 converged as DEFAULT with the following host(s) as part of the cluster: 2





CAUSE
This issue occurs if the cluster hosts do not detect the cluster heartbeat messages that are sent from other Network Load Balancing cluster hosts. This issue may be caused by a cluster configuration issue, or by a hardware or a driver issue such as a network adapter problem, an incompatible network adapter driver, or a problem with the hub or the switch that connects the Network Load Balancing cluster hosts.



RESOLUTION
To resolve this issue, follow these steps:  Verify the Network Load Balancing configuration.

For additional information about how to do this, click the following article numbers to view the articles in the Microsoft Knowledge Base:

197992 How to configure WLBS using a single network interface card

256124 How to configure an IP address for NLB with one network adapter

256910 IP address assignment for nlb with multiple network adapters

303608 How to configure Network Load Balancing parameters in Windows 2000

 Verify the number (NumberOfRules) and type of port rules (PortRules) on each cluster host.

Each host must have the same number and type of port rules. Additionally, the host priorities (HostPriority) must not overlap. To view the configuration of a Network Load Balancing cluster host, run the WLBS display command from a command prompt. The following is an example of the output from this command:

<pre class="fixed_text">=== Configuration: ===

HostPriority           = 2 NumberOfRules          = 1 PortRules Virtual IP addr Start End     Prot   Mode        Pri    Load    Affinity

ALL     0  65535   Both   Multiple           Equal   C

00000000 0000FFFF 6FFFF000 00000002 00000003 00000001 00010001 00000000

Compare the HostPriority, NumberOfRules, and PortRules results for each cluster host.</li> View the Microsoft Windows 2000 Event Viewer to determine if a host is in conflict with another cluster host.</li> Reduce the Network Load Balancing hardware configuration to the simplest possible configuration.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

247297 Network Load Balancing connection to a Virtual IP address not made across a switch

</li> Make sure that you are not using a crossover cable between the private network adapters in the cluster.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

242248 Using crossover cable causes load balancing not to work

</li> If you use a layer 2 switch to connect the Network Load Balancing hosts in unicast mode, make sure that you can pass broadcast packets. If this feature is not enabled, the heartbeat packets cannot be detected by other hosts. This causes the hosts to converge only with themselves.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

238219 How NLB hosts converge when connected to a Layer 2 switch

</li> Replace the switch that connects the private network adapters in the cluster with a hub. Connect the hub to the uplink port on the switch. If you already use a hub to connect the private network adapters, set the  registry value to 0 (zero).

For additional information, click the following article numbers to view the articles in the Microsoft Knowledge Base:

193602 Configuration options for WLBS hosts connected to layer 2 switches

303765 How to perform Advanced Network Load Balancing procedures in Windows 2000

Note Some switches are reported to cause problems with Network Load Balancing clusters.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

247297 Network Load Balancing connection to a Virtual IP address not made across a switch

Additionally, some hubs have built-in switch functionality--for example, the 3COM Superstack dual-speed hub 3C16592B. Some network adapters may not be able to autosense the network transmission speed correctly. It may be best to manually configure the network speed for the network adapters on all cluster hosts.</li> If the cluster hosts have Gigabit network adapters, verify that they are listed on the hardware compatibility list (HCL).

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

309395 The Microsoft support policy for server clusters, the Hardware Compatibility List, and the Windows Server Catalog

</li> Check the Gigabit Server Adapter properties. The network adapter driver may prevent hosts from overwriting the real Media Access Control (MAC) address with the address that is used for Network Load Balancing (the ClusterNetworkAddress entry that is returned when you run the WLBS display command). This MAC address is in the format of 02-BF- - - -  where - - -  is the cluster virtual IP address in hexadecimal notation. For example, 02-BF-0A-A5-02-13 corresponds to IP address 10.165.2.19.

If you are using Network Load Balancing in unicast mode, you may have to manually set the network adapter's Locally Administered Address (LAA) to the Network Load Balancing cluster unicast MAC address (ClusterNetworkAddress). You must do this by using the driver program for the load-balanced network adapter on each host in the cluster. You must not set the LAA for Network Load Balancing clusters that are operating in multicast mode.</li> Verify that you are running the latest network adapter drivers.</li> Make sure that you are not using fault tolerant or teaming network adapters. If you are using teaming network adapters, disable teaming mode for the duration of the troubleshooting process.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

278431 Using teaming adapters with network load balancing may cause network problems

</li> If your Network Load Balancing cluster has two nodes, stop the node that works correctly. To do so, follow these steps: <ol style="list-style-type: lower-alpha;"> From a command prompt, type the following, and then press ENTER:

wlbs stop

</li> On the remaining cluster node, type the following command, and then press ENTER:

wlbs query

If the host does not converge with itself, or with other cluster nodes, follow these steps: <ol> Obtain and install the latest network adapter drivers, or if this is a Compaq computer the latest SoftPack.</li> Test Network Load Balancing.

If it does not work successfully, disable the fault-tolerant teaming mode (if applicable) on the network adapters, and then re-test Network Load Balancing.</li> If you are unsuccessful, remove the network adapter device by using Device Manager.

Restart the server and permit Windows to detect the network adapter drivers. Reconfigure Network Load Balancing by using a virtual and a dedicated IP address.</li></ol> </li></ol> </li> <li>Capture a network trace on the cluster network adapters.

The Microsoft Windows 2000 Server Resource Kit includes a Microsoft Network Monitor parser for Windows Load Balancing Server and Network Load Balancing traffic (Wlbs_hb.dll and Wlbs_rc.dll). You can use this for additional troubleshooting.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

280503 Additional Network Monitor Parsers Included in the Microsoft Windows 2000 Server Resource Kit

</li></ol>

After you have successfully configured the Network Load Balancing cluster, run the following command:

wlbs query

When you run this command on the default host in a two-node cluster, you receive results that are similar to the following:

<pre class="fixed_text">WLBS Cluster Control Utility V2.4 (c) 1997-2003 Microsoft Corporation.

Host 1 converged as DEFAULT with the following host(s) as part of the cluster: 1,2

When you run this command on another host in the two-node cluster, you receive results that are similar to the following:

<pre class="fixed_text">WLBS Cluster Control Utility V2.4 (c) 1997-2003 Microsoft Corporation.

Host 2 converged with the following host(s) as part of the cluster: 1,2

<div class="moreinformation_section">

MORE INFORMATION
The number and type of rules must be exactly the same for each host in the Network Load Balancing cluster. If a host tries to join the cluster by using a different number of rules from the other hosts, it is not accepted as part of the cluster and the rest of the cluster continues to handle the traffic as before. At the same time, a message is logged in the Windows event log. If this issue occurs, see the Windows 2000 event log to determine the host that is in conflict with the other cluster hosts, resolve the conflict, and the restart Network Load Balancing on that host.

Convergence
Network Load Balancing hosts periodically exchange multicast or broadcast heartbeat messages in the cluster. This permits them to monitor the status of the cluster. When the state of the cluster changes (such as when hosts fail, leave, or join the cluster), Network Load Balancing invokes a process that is known as convergence. During convergence, the hosts exchange heartbeat messages to determine a new, consistent state of the cluster and to elect the host with the highest host priority as the new default host. When all cluster hosts have reached consensus on the correct new state of the cluster, they record the change in cluster membership in the Windows 2000 event log when convergence is complete.

If a host tries to join the cluster by using inconsistent port rules or an overlapping host priority, convergence cannot be completed.

The third-party products that are discussed in this article are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.

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