Schneider Electric 840 USE 106 0 manual Overview of Hot Standby Solution for NOEs, Please Note

Ethernet Hot Standby Solution

Overview of Hot Standby Solution for NOEs

Please Note	The Quantum Hot Standby system supports up to four NOE 771 Ethernet
	connections. For a more detailed description of the physical set up of a Hot Standby
	system, refer to the Quantum NOE 771 xx Ethernet Modules User Guide,
	840USE11600, Chapter 9, "Hot Standby".
Description of
	The Hot Standby solution provides bumpless transfer of I/O using remote I/O. The
the Hot Standby	NOE Hot Standby support now allows automation IP Address change. Both
Solution	controllers are configured identically. One controller is the Primary NOE; the other
	controller, the Secondary NOE. In case of a failure, the controllers switchover and
	the system recovers quickly.
	The NOEs coordinate the swapping of IP addresses. After closing both the client
	and the server connections, each NOE sends a swap UDP message to its peer
	NOE. The sending NOE then waits a specified timeout (500 ms) for the peer swap
	of UDP messages. Either after receiving the messages or after a timeout, the NOE
	changes its IP address.

Note: NOEs must communicate with each other in order to swap IP Addresses. Schneider Electric recommends that you connect the primary and Secondary NOEs to the same switch because

lCommunication failures between the NOEs increases the time to swap Connecting two NOEs to the same switch, minimizes the probability of a communication failure

Note: Schneider Electric recommends that a switch is used to connect the NOEs to each other or to the network. Schneider Electric offers switches; please contact a local sales office for more information.

The NOE waits for either a change in the controller’s Hot Standby state or the swap of UDP messages. Then the NOE performs one of two Hot Standby actions.

If the NOE:

1.Detects that the new Hot Standby state is either primary or standby: The NOE changes the IP address

2.Receives a swap UDP message:

The NOE transmits a Swap UDP message and swaps the IP address

164 840 USE 106 00 January 2003