MACROMEDIA COLDFUSION 4.5-ADMINISTRING COLDFUSION SERVER Manual page 188

166 Administering ColdFusion Server
Configuring DNS records on your primary DNS server
You must configure DNS so that both the forward and reverse lookup translation
entries are entered and registered correctly with your primary DNS server. To
accomplish this, you must define required DNS records (A records and PTR records)
for your Web servers on your primary DNS server.
Besides standard name translations, your primary DNS server can also distribute
HTTP requests sequentially across clustered servers using a technique called round-
robin DNS. This service allows DNS to return a list of multiple servers back to the
browser that requests a name translation.
Round-robin DNS and ClusterCATS work well together. You don't want to rely on just
round-robin DNS for distributing load for your business-critical sites because DNS
functionality is limited. In short, DNS is a good load distribution technique, but it
cannot manage load because it is unable to react to increases in server traffic. It also
cannot detect server failures nor redirect requests among available servers.
ClusterCATS compensates for these limitations.
Allaire recommends that you use round-robin DNS or a hardware load balancing
device to distribute requests initially to the Web servers in your cluster. Following the
initial distribution, the ClusterCATS load management and failover features
automatically take over and ensure that your ColdFusion applications remain up and
running.
Using ClusterCATS with round-robin DNS
So that ClusterCATS operates effectively with round-robin DNS, you need to ensure
that round-robin DNS entries are configured correctly on your primary DNS server.
For example, for a single-location server cluster consisting of four servers, you need to
configure round-robin DNS across all four servers for the domain name and individual
IP addresses for each explicit server name. As an example, your DNS tables on your
primary DNS server would look similar to the tables that follow.