Having comm failure with remote sites in SCADA network. Using 900 mHz radio's to communicate, Modicon M340 PLC and Magelis OIT for RTU and local interface. When comm condition occurs, have found disconnecting OIT from the Ethernet switch clears issue. However, this condition is moving from site to site, and we have not been able to identify why the comm failure is happening. Any help is appreciated.

 

Some Radio links may 'disconnect' when carrier is lost and then reconnect to the network. If DHCP is in use without leases, then this will wreak havoc with automatic switches.

For a quick test, try it with an old non switching hub if you have one.

Control networks generally use static IP addressing, and although this may ease the symptoms, you should also check why you are losing the carrier.