User Guide

Chapter 6: Creating Scalable and Highly Available Web Sites 167
Note When using round-robin DNS, do not define a reverse mapping (PTR
record) for the site name (www.company.com); the cluster will not
operate properly if you do. Only define forward mappings (A records) for
www.company.com. However, define both A records and PTR records for
all of the explicit servers (www1, www2,...) in the cluster. This
configuration ensures that requests cycle through the servers
sequentially in round-robin fashion.
Round-robin DNS distributes the initial domain-level requests across all four servers.
Thereafter, ClusterCATS distributes load to avoid failed or overloaded servers.
To configure DNS records on your Windows NT DNS server:
1. On your primary DNS server, click Start>Administrative Tools>DNS Manager.
Forward DNS Entries with Round Robin Enabled
Host Name IP Address
www.company.com 193.168.0.1
193.168.0.2
193.168.0.3
193.168.0.4
www1.company.com 193.168.0.1
www2.company.com 193.168.0.2
www3.company.com 193.168.0.3
www4.company.com 193.168.0.4
Reverse DNS Entries for Explicit Server Names
IP Address Host Name
193.168.0.1 www1.company.com
193.168.0.2 www2.company.com
193.168.0.3 www3.company.com
193.168.0.4 www4.company.com