The Series 90 TCP/IP Triplex Communications enabler can be configured for one or two network communications paths to each device in a PLC group.
CIMPLICITY normally uses the primary cable address and monitors the secondary. If the primary cable address fails, the enabler automatically switches to the secondary. The enabler continues to monitor the primary and will automatically switch back should it recover.
Cabling redundancy can be implemented with:
One Ethernet LAN with two connections from each PLC to the Ethernet LAN.
A redundant Ethernet LAN and one connection from each PLC to both of the Ethernet LAN's.
When multiple Ethernet cards are used in the host computer, the Host IP Address and PLC IP Address in combination with the Subnet Mask of the Ethernet card determines which card/cable combination will be used.
Series 90 TCP/IP redundancy overview.