I agree. If you absolutely have to use your plant network, at least use two firewalls to set up an encrypted VPN between the PLCs. If you have tight timing requirements you may have to use a dedicated link anyway. Also, depending on the criticality of the application, you may want to implement a watchdog, so if the destination PLC does not get an update from the source PLC in a certain amount of time, some fail-safe action is taken by the PLC logic. Corey Clingo BASF From: Ken Heywood <KHeywood@xxxxxxxxxxxxxxxxxxxxxxxxxx> To: "foxboro@xxxxxxxxxxxxx" <foxboro@xxxxxxxxxxxxx> Date: 06/20/2012 08:50 AM Subject: Re: [foxboro] Connecting two PLC through Plant Network Sent by: foxboro-bounce@xxxxxxxxxxxxx It's a dangerous practice to run process control over the general purpose plant network. Run a separate network or secure radio link. Using the plant network leaves you open to intended and non-intended unauthorized access to your production system. Always connect process network to plant network through an application gateway, firewall or secure router. Thank You, Ken Heywood Calibration Laboratory Manager PROCESS CONTROL SERVICES, INC. Established in 1983 http://www.processcontrolservices.com mailto:KHeywood@xxxxxxxxxxxxxxxxxxxxxxxxxx Telephone: 734-453-0620 Wireless: 508-241-2040 _______________________________________________________________________ This mailing list is neither sponsored nor endorsed by Invensys Process Systems (formerly The Foxboro Company). Use the info you obtain here at your own risks. Read http://www.thecassandraproject.org/disclaimer.html foxboro mailing list: //www.freelists.org/list/foxboro to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave