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Configuring MODBUS TCP
Configuring the Switch as the MODBUS TCP Server
!
access-list 101 permit tcp 10.1.1.0 0.0.0.255 any eq 502
Multiple Request Messages
The switch can receive multiple request messages from clients and respond to them simultaneously.
You can set the number of client connections from 1 to 5. The default is 1.
Configuring the Switch as the MODBUS TCP Server
Defaults, page 988
Enabling MODBUS TCP on the Switch, page 988
Defaults
The switch is not configured as a MODBUS TCP server.
The TCP switch port number is 502.
The number of simultaneous connection requests is 1.
Enabling MODBUS TCP on the Switch
Beginning in privileged EXEC mode:
To disable MODBUS on the switch and return to the default settings, enter the no scada modbus tcp server global
configuration command.
To clear the server and client statistics, enter the clear scada modbus tcp server statistics privileged EXEC command.
After you enable MODBUS TCP on the switch, this warning appears:
WARNING: Starting Modbus TCP server is a security risk.
Please understand the security issues involved before
proceeding further. Do you still want to start the
server? [yes/no]:
Command Purpose
1. configure terminal Enters global configuration mode.
2. scada modbus tcp server Enables MODBUS TCP on the switch
3. scada modbus tcp server port
tcp-port-number
(Optional) Sets the TCP port to which clients send messages.
The range for tcp-port-number is 1 to 65535. The default is 502.
4. scada modbus tcp server
connection connection-requests
(Optional) Sets the number of simultaneous connection requests
sent to the switch. The range for connection-requests is 1 to 5.
The default is 1.
5. end Returns to privileged EXEC mode.
6. show scada modbus tcp server Displays the server information and statistics.
7. copy running-config startup
config
(Optional) Saves your entries in the configuration file.
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