GE PACSystems RX7i, User Manual

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Chapter 1. Introduction
GFK-2224Q January 2017 15
Web Server Operation in a Redundancy System
Only the active unit processes Web server requests at the Redundant IP address and responds to Web page
requests. The backup unit does not respond to the Redundant IP address. When the active Ethernet interface
changes to backup, it takes down all Web server connections and their underlying TCP connections. The Web
server maintains its underlying TCP connection only long enough to process each web page request; a new TCP
connection is opened, used, and closed for each subsequent Web page display or update. So unless a Web page
change or update is requested during the redundancy role switch, the operation of the Redundant IP address is
transparent to the Web remote browser. Any Web page request in process over the Redundant IP when a role
switch occurs is terminated.
Although not recommended, the remote browser may issue Web server requests to the direct IP address. Both
the active and backup units respond to Web server requests received at the direct IP address. Remote Web
browsers are expected to use the Redundant IP address when communicating to a redundant system.
FTP Operation in a Redundancy System
FTP operations are used to transfer setup and configuration data to the Ethernet interface, not for
communication with the actual PLC application. Therefore, FTP operations should only be performed using the
direct IP address.
SNTP Operation in a Redundancy System
A PACSystems Ethernet Interface can operate as an SNTP client only, so it only receives broadcast time
messages from an SNTP Server on the network. SNTP operation is unaffected by the current Ethernet
redundancy state or by redundancy role switches.
Remote Station Manager Operation in a Redundancy System
The remote Station Manager should respond to the direct IP address regardless of whether the unit is active or
backup, or whether or not Redundant IP is configured.
Only the active unit responds to remote Station Manager commands at the Redundant IP address. The backup
unit does not respond to the Redundant IP address. (Station Manager responses from the Redundant IP address
can be misleading because it is difficult to determine which Ethernet interface is actually responding.)
IP Address Configuration in a Redundancy System
Redundancy systems should explicitly configure both the direct IP address and the Redundant IP address. Do
not set up the direct IP address via BOOTP.
The Redundant IP address must be configured on the same local sub-network as the direct IP address and
gateway IP address (if used).