There are three cluster roles available when you configure the ADC for high availability.
Cluster
By default, a new ADC will power on using the Cluster role. In this role, each cluster member will have the same “working configuration,” and as such, only one ADC in the Cluster will be Active at any one time.
A “working configuration” means all configuration parameters, except items that need to be unique such as the management IP address, ALB Name, network settings, interface details, and so on.
The ADC in priority 1, the topmost position, of the Cluster Members box is the Cluster Owner and the Active load balancer, while all other ADC’s are Passive members.
You can edit any ADC in the Cluster, and the changes will be synchronized to all Cluster members.
When you remove an ADC from the Cluster, all Virtual Services will be deleted from that ADC.
You cannot remove the last member of the Cluster to Unclaimed Devices. To remove the last member, please change the role to Manual or Stand-alone.
The following objects are not synchronized:
o Manual Date & Time section – (NTP Section is synchronized)
o Failover Latency (ms)
o Hardware section
o Appliance section
o Network section
Failure of the Cluster Owner
When a cluster owner fails, one of the remaining members will automatically take over and carry on load balancing the traffic.
When the cluster owner returns, it will resume load balancing traffic and take over the owner role.
Let’s assume the Owner has failed, and a Member has taken over the load balancing. If you would like that Member that has taken over load balancing traffic to become the new owner, highlight the member and click the up arrow to move it to the Priority 1 position.
If you edit one of the remaining cluster members and the owner is down, the edited member will automatically promote itself to the owner without loss of traffic
Changing role from Cluster role to Manual role
If you wish to change the role from Cluster to Manual, click the radio button next to the Manual role option
After you click the radio button, you will see the following message:
Click the OK button
Check the Virtual Services section. You will find that the Primary column now shows an unticked box.
It is a safety feature and means that if you have another ADC with the same Virtual Services, then there will be no interruption to traffic flow.
Changing role from Cluster to Stand-alone
If you wish to change the role from Cluster to Stand-alone, click on the radio button next to the Standalone option.
You will be prompted with the following message:
Click OK to change roles.
Check your Virtual Services. You will see that the Primary column change name to Stand-alone
You will also see that all the Virtual Services are disabled (un-ticked) for safety reasons.
Once you are confident that no other ADC on the same network has duplicate Virtual Services, you can enable each one in turn.
Manual Role
An ADC in the Manual role will work with other ADC’s in the Manual role to provide high availability. The main advantage over the Cluster role is the ability to set which ADC is Active for a Virtual IP. The disadvantage is that there is no configuration synchronization between the ADC’s. Any changes must be replicated manually on each box via the GUI, or for lots of changes, you can create a jetPACK from one ADC and send this to the other.
To make a Virtual IP address “Active”, tick the checkbox in the primary column (IP Services page)
To make a Virtual IP address “Passive”, leave the check-box blank in the primary column (IP Services page)
In the event, an Active service fails over to the Passive:
o If both Primary Columns are ticked, then an election process takes place, and the lowest MAC address will be Active
o If both are un-ticked, then the same election process takes place. In addition, if both are un-ticked, there is no automatic fallback to the original Active ADC
Stand-alone Role
An ADC in the Stand-alone role will not communicate with any other ADC regarding its services, and therefore all Virtual Services will remain in the Green status and connected. You must ensure that all Virtual Services have unique IP addresses, or there will be a clash on your network.
