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The Balancing Act: Installing Windows NLB for Web servers

 

Shijaz Abdulla, MVP www.shijaz.com/windows

 

 

This article gives step-by-step explanation on how to setup Network Load Balancing (NLB) using Windows 2003 Network Load Balancing components.

 

Background

 

You can use NLB to “balance” request traffic (load) between two or more servers. This article explains how to implement it and assumes that you know what NLB is for. If not, please see the links in the “Prerequisites” section.

 

Prerequisites

 

Make sure you read and understand the following Microsoft articles:

 

• Windows NLB FAQ page:

http://www.microsoft.com/technet/prodtechnol/windowsserver2003/technologies/clustering/nlbfaq.mspx

 

• Understanding Windows NLB

http://technet2.microsoft.com/WindowsServer/f/?en/Library/088a26d1-1d67-45a3-8d89-e7a056c1c1131033.mspx

 

Assumptions

 

Below is a brief outline of the lab scenario employed in this article:

 

Server1: OS: Windows Server 2003 Standard Hostname: TESTDC01.testdomain.local No. of Network adapters: 2   Public Interface: NIC1 IP on NIC1: 192.168.10.1 DNS: 192.168.10.1   Private Interface: NIC2 IP on NIC2: 10.0.0.2	Server2: OS: Windows Server 2003 Standard Hostname: EXCHANGE01.testdomain.local No. of Network adapters: 2   Public Interface: NIC1 IP on NIC1: 192.168.10.2 DNS: 192.168.10.2   Private Interface: NIC2 IP on NIC2: 10.0.0.1
NLB Virtual Virtual Hostname: CLUSTER.testdomain.local Virtual IP: 192.168.10.100

 

 

Configuration required on Server1

 

Step 1.         Install IIS

 

For step-by-step instructions on how to install IIS, see Windows Help.

 

Step 2.         Create a new NLB cluster

 

 

 

1. Open the Network Load Balancing Manager. Start à Administrative Tools à Network Load Balancing.

 

2. Choose Cluster à New

 

3. Enter the information as below:

 

1. Cluster IP configuration > IP Address: Enter the “Virtual” IP of your cluster. This is the NLB IP on which clients will connect. It should not be already in use on your network and must belong to the same subnet as your web servers.
   
   
2. Cluster IP configuration > Subnet Mask: Enter the subnet mask for your virtual IP. Should be same as what you use on the network containing your web servers.

 

3. Cluster IP configuration > Full Internet name: Enter the full DNS “virtual” name of your NLB cluster. Your clients will connect to this hostname. Please note that NLB manager does not automatically register this name in DNS, you will have to do it manually as explained later in this article.

 

4. Select Multicast. For more information on Unicast and Multicast, see the Microsoft article.

 

 

4. Click Next.
5. If you need to add any additional virtual IPs for your cluster, enter them in the screen below, else click Next.

 

 

 

 

 

6. Configuring Port Rules: Here you can specify whether to load balance traffic only for specific ports or to load balance all traffic. In this scenario, you can choose to load balance only port 80 (http) traffic.

 

 

7. Click Next. In the next screen you will be prompted to enter hostname of first node in the cluster. Enter the hostname of the machine you are working on and click Connect. You will be displayed the interfaces available on the computer. Select the interface that you want to load balance, i.e. Public interface of the host.

 

 

 

8. Click Next. In the next screen you see the host parameters for this configuration. Review them and click Next.

 

 

9. You will see the progress of adding the host on the new cluster in the NLB manager window. Wait until the status of the host is Converged.

 

 

 

 

Step 3.         Add second host to the NLB cluster

 

 

1. In the Network Load Balancing Manager, right click on the cluster and choose “Add Host to Cluster”.

 

2. In the Network Load Balancing Manager, right click on the cluster and choose “Add Host to Cluster”.

 

3. Type the name of the second node and click Connect. Select the Public interface on the second node and choose Next.

 

 

 

4. Review the host parameters and click Next.

 

 

 

 

5. NLB manager will show the progress as the second node is being added to the cluster. Wait until status is Converged for both nodes.

 

 

 

6. To test NLB, connect to the virtual IP from the browser of any client connected to the network. You should get the webpage even if one of the nodes is shut down.

 

Step 4.         Register NLB virtual name in DNS

 

 

1. On your DNS server/domain controller, open the DNS management console. Start à Administrative Tools à DNS.

 

 

2. Expand you Forward Lookup Zone, right click on your domain’s DNZ zone and click New Host (A) option.

 

3. Enter the details as follows:

 

1. Name: Enter the virtual hostname you used in step 1.3 (d) (in this case, “cluster”)
2. IP address: Enter the virtual IP of the cluster you used in step 1.3 (a) (in this case, “192.168.10.100”)
3. If you require a PTR record in your RDNS, select the option.
4. Click Add Host.

 

 

 

 

 

Troubleshooting tips:

 

• Sometimes while adding the second node, the process may fail and you will not see the status “Converged”, instead you will find a yellow exclamation mark next to the second node. In this case, right click on the node and choose Delete. Then login to the second node directly and use the NLB manager on the second node itself. Choose Cluster à Connect to Existing and type host name of the first node. Then continue the process, working from the second node itself.
• At times you might get an error NLB not bound and an error code. In such cases, check the following:
• IP addresses and subnet masks on public interface of both nodes and virtual IP of cluster.
• On the node that is failing see if the Public interface has more than one IP address?
• Network Load Balancing service is installed on the public interface?

 

See also: Windows NLB: The Ultimate FAQ

 

 

 

 

 

Disclaimer

The steps mentioned in this are results of testing in a lab environment. The procedure might require additional testing before being deployed on a production environment. I assume no responsibility for damage(s) occurring due to following this procedure or any other procedure listed on this site. Use it at your own risk!