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Setting up Redundancy

To set up redundancy, you first must understand that both of the nodes share the exact same configuration state. This means that when a backup node joins to a master node, it will essentially download a backup of the master's state and restore that backup on itself. This fact leads to a couple of observations:

 

1.It is best to start with a fresh install for the backup node. The current configuration of the backup node will be overwritten, so make sure that it does not contain anything valuable in it when enabling redundancy.
2.All system configuration relative to the master node must also resolve on the backup node. For example, OPC-UA connections and database connections must use addresses that resolve from both nodes, any OPC-COM servers must be installed and configured identically on both nodes, etc.

 

With that in mind, setting up redundancy is fairly simple. Follow these steps to set up your redundant pair:

 

1.Turn off firewalls between the redundancy nodes. Redundant systems need TCP connectivity between each other on a variety of ports. Turning off software firewalls or adding special exception rules for each others' addresses is required. Specifically, The master node must be able to receive data on TCP/IP port 8750 (changeable in settings), and the backup node must be able to send outgoing data on that port.
2.Configure the master node.
2.1. Set mode to 'Master' under the Configuration > Redundancy in the gateway configuration.
2.2. It is advisable to turn off 'Auto-detect network interface' and to manually specify the address of the NIC (network interface card) to use for communication.
2.3. The addition settings are described in the next section, redundancy settings.
3. Configure the backup node
3.1. On the desired backup system, set the mode to 'Backup'.
3.2. Under 'Backup Node Settings', specify the address of the master node. Also verify that the port is correct under 'Network Settings'.
3.3. After saving, the system will connect to the master and will download a system backup, which will trigger a restart. After the restart is complete, the backup node should now be synchronized and in communication with the master.
4.Verify Redundancy Setup with the System Map. When you go to the status section of the gateway, the system map should show both connected nodes and should show their current states.