From brokenpoet.org wiki

In this example We will have 8 machines, broken down to 3 DNS machines and 5 hosting machines. We will label them as:

DNS1 = DNS Machine
DNS2 = DNS Machine
DNS3 = DNS Machine

SERVER1 = Hosting Server
SERVER2 = Hosting Server
SERVER3 = Hosting Server
SERVER4 = Hosting Server
SERVER5 = Hosting Server

Firstly, the DNS Servers (DNS1-3) will be exclusively DNS servers. No hosting will happen on these servers.

Login to WebHostingManager on each Hosting Server (SERVER1-5), navigate to the Cluster Managerment area and ADD DNS1 to each (You may need to go to DNS1 and mutually add a remote key for SERVER1-5).

Now set DNS1 as synchronizing in each of the hosting servers (SERVER1-5).

Next, You will now go to DNS1's WHM and enter the cluster management area, you should see SERVER 1-5 listed as standalone servers. Now add DNS2 and DNS3 to the cluster (You may need to login to DNS2 and DNS3 and mutually add DNS1 to the respective cluster)

After Added, You will set DNS2 and DNS3 to Synchronize Changes.

Follwoing this, load DNS2 and DNS3's WHM and go into the cluster management area and set each to synchronize with DNS1

You should now see the following on each servers:

DNS1: All servers in cluster listed, SERVER1-5 (standalone) and DNS2-3 (synchronize)
DNS2: DNS1 listed to Synchronize
DNS3: DNS1 listed to Synchronize

SERVER1: SERVER1 listed to Synchronize
SERVER2: SERVER1 listed to Synchronize
SERVER3: SERVER1 listed to Synchronize
SERVER4: SERVER1 listed to Synchronize
SERVER5: SERVER1 listed to Synchronize