Installing a front-end load balancer (optional)

You install a load balancer in front of the web servers in an IBM® WebSphere® Application Server cluster installation if your installation requires very high availability. This configuration is called an IP sprayer topology.

About this task

Steps for installing a front-end load balancer are specific to external vendors and are not provided in this documentation.

Do not install a load balancer directly in front of a WebSphere Application Server cluster without a web server between the load balancer and the cluster. Web servers with the WebSphere Application Server workload management plug-in adjust to changes in the cluster topology such as adding or removing nodes. Load balancers do not have this functionality, and must be manually reconfigured.

Make sure to configure session affinity in the load balancer. There are several methods to achieve session affinity. The method that you choose depends on the product that you use and the forwarding mechanism that you configure. Mechanisms include media access control (MAC) address forwarding, Network Access Translation/Network Address Port Translation (NAT/NAPT) forwarding, and content-based forwarding. Layer 2 load balancers (load balancers that operate at the MAC layer) generally achieve session affinity by using a stickiness to source IP address approach. Layer 3 and higher load balancers (load balancers that operate at the IP layer and above) typically achieve session affinity by using passive cookies or a content-based technique. Session affinity with HTTP servers is typically achieved by using these techniques.

What to do next

After you install a load balancer, you can install any additional components that you need, such as backup load balancers and firewalls.