Host Engineering Forum
General Category => General Discussion => Topic started by: jamesdavid on October 20, 2026, 06:47:16 PM
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I’ve lost a fair bit of time chasing connection problems that turned out to be the PC and not the PLC. What usually fixes it for me is setting a static IP in the PLC’s subnet, turning off Wi-Fi so traffic doesn’t go out the wrong adapter, and pinging the PLC before touching the software. After that, I check whether the firewall is blocking the programming software and whether the software version matches the PLC firmware. I also run a separate PC for logging and simulation, and I picked up refurbished datacenter hardware (https://www.orangehardwares.com/collections/refurbished-servers) for it, which has been solid and a lot cheaper than new, though it’s worth checking that the NIC and OS work with your tools. Curious what other PC-side got chas people have run into.
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DHCP on your PC (Client) is OK.
DHCP on your PLC (Server) is usually NOT good (because the assigned IP Address can change, and Designer's Connection Link cannot resolve its mapped IP Address).
Do-more Designer can handle multiple subnets on your PC. The Select Connection/Link dialog lets you choose the set of NIC/Subnets to support. You typically have just 1 subnet for your OT and a DIFFERENT subnet for your IT. Make sure the subnets are DIFFERENT (not just a different IP Address), e.g.
192.168.10.9 subnet mask 255.255.0.0 (so subnet 192.168.x.x)
172.10.1.42 subnet mask 255.255.255.0 (subnet 172.10.1.x)
172.10.2.42 subnet mask 255.255.255.0 (subnet 172.10.2.x)
Hit the Select Ethernet Networks button and check the one(s) with PLCs on them, and UNcheck the ones without.