IP Address Assignment

Overview

The ETY TCP/IP address must be configured in Control Expert. Since the primary and standby controllers must have an identical configuration, the configured IP addresses will be the same. The ETY’s IP address is either the configured IP address or the configured IP address + 1.

The IP address is determined by the current local Hot Standby state. In the offline state, the IP address is determined by whether or not the standby PLC is in transition to the primary state. In a Premium Hot Standby System, the two IP addresses are consecutive.

Address Assignments

The following table shows the IP address assignments.

Hot Standby State	IP Address
Primary	Configured IP address
Standby	Configures IP address + 1
Transition from primary to offline	Configured IP address, if peer PLC does not go to primary
Transition from standby to offline	Configured IP address + 1.

NOTE: Offline results depend on whether or not the PLC is detected to be in transition into the primary state. If the current IP is the configured IP address and the other PLC is in transition to primary, then the IP address changes to IP address + 1.

Restrictions

Do not configure the ETY module to obtain an IP address from a server.
Assign IP addresses that are in the same network and subnetwork to the primary and the standby ETY modules.

NOTE: Duplicate IP address checking is performed only at power-up of the hot standby PLC. It is not performed during a switchover or after the removal or replacement of the ETY Ethernet cable.

IP Address Transparency

CAUTION

UNEXPECTED EQUIPEMENT OPERATION

For a Premium Hot Standby configuration:

Do not use consecutive IP addresses for consecutive ETY modules configured.
Do not configure the primary address as nnn.nnn.nnn.254. This causes the standby IP address to be: nnn.nnn.nnn.255. The ETY would then return the diagnostic code Bad IP configuration.

Failure to follow these instructions can result in injury or equipment damage.

For continued Ethernet communication, the new primary ETY must have the same IP address as the former primary ETY. The IP address in the standby ETY is the primary IP address + 1.

The ETYs integrated into the Premium Hot Standby configuration coordinate this IP address swapping with the management of Ethernet services used.

If the ETY detects a duplicate IP address when it powers up, the PLC goes to its offline state and the ETY’s IP address goes to its default setting.