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Ethernet Hot Standby Solution
174
840 USE 106 00 January 2003
Network Effects of Hot Standby Solution
Overview The Hot Standby solution is a powerful feature of NOEs, a feature that increases the
reliability of your installation. Hot Standby uses a network, and using the Hot
Standby feature over a network can affect the behavior of
Browsers
Remote and Local clients
I/O Scanning service
Global Data service
FTP/TFTP server
The following are factors you may encounter while using the Hot Standby solution.
Browsers
If a browser requests a page and during the process of downloading that page an IP
Address swap occurs, the browser will either hang or time out. Click the Refresh or
Reload button.
Remote Clients Hot Standby swaps affect remote clients.
An NOE will reset under the following conditions:
Remote Connection Request during Hot Standby Swap
If a remote client establishes a TCP/IP connection during a Hot Standby swap,
the server closes the connection using a TCP/IP reset.
Hot Standby Swap during Remote Connection Request
If a remote client makes a connection request and a Hot Standby swap occurs
during the connection request, the sever rejects the TCP/IP connection by
sending a reset.
Outstanding Requests
If there is an outstanding request, the NOE will not respond to the request, but
the NOE will reset the connection.
The NOE will do a Modbus logout if any connection has logged in.
Local Clients During a swap, the NOE will reset all client connections using a TCP/IP reset.
Note: In Hot Standby configuration the NOE’s I/O scanner is enabled.