User manual

Hot Standby
33002479 06 07/2008 311
The NOE waits for either a change in the controller’s Hot Standby state or the swap
of UDP messages. Then the NOE performs 1 of 2 Hot Standby actions.
All client/server services (I/O scanner, global data, messaging, FTP, SNMP, and
HTTP) continue to run after the switch from the old to the new primary NOE.
Hot Standby and
NOE Module
Functionality
The following table identifies the Ethernet services that are available and
unavailable in a hot standby solution.
Note: Schneider Electric recommends that you use a switch (not a hub) to connect
the NOEs to each other or to the network. Schneider Electric offers switches;
please contact a local sales office for more information.
If the NOE . . . Then
Detects that the new Hot Standby state is
either primary or standby
The NOE changes the IP address.
Receives a swap UDP message The NOE transmits a Swap UDP message
and swaps the IP address.
Note: Failure of an NOE module is not a condition for the primary system to leave
the primary state.
Service NOE 771 Family
I/O Scanning Available
Global Data Available
Modbus Messaging Available
FTP/TFTP Available
SNMP Available
HTTP Server Available
DHCP Unavailable
Note: Only the 140 NOE 771 01 or 140 NOE 771 11 (TCP/IP Ethernet modules)
support a Modicon Quantum Hot Standby with Unity V2.0 system.