..All the documentation tells you this ...
I know .. RTFM ..
in my defence, locating the FM sometimes takes a bit of effort
So instead, troubleshoot the 1756-EN2T installation, which appears to be telling you plainly and correctly that it can't connect to the NTP server.
Yup, that's why I tried it.
I think I mentioned, I'm located remote. I can't change out the ethernet card that is connected to the Control Domain until I drive to site. The EN2T/D is connected to IO, and I could steal it for testing .. if I drove out there. The plant does not have many places to actually use an ENBT/A, so it is likely to stay where it is longer term (except for testing)
The VM running Studio is on the Control Domain and can ping the NTP server and the ENBT. The only thing holding me back there *COULD* be the firewall, as the VM is on a different subnet than the ENBT. The layer 3 switch or the firewall *COULD* prevent the Control Domain VLAN from communicating. I doubt it, but it could.
And I would install another computer or device that is known to have a functional NTP client (like your Windows PC running its own time client, or something like the
NIST time client) as close to the -EN2T as possible, including literally plugging into the same Ethernet port with the same cable.
Good ideas, but I have some limitations. There is only the one port on one switch in that test area that is part of the Control Domain VLAN. The IT guys are quite paranoid, so I'm not sure if I can even change out the ENBT/A to an EN2T without their help. But I'll try that first when I get to site.
Some days it might just be faster and easier to test things out on the production PLCs (but I won't)
EDIT: I guess I never mentioned that we had an EWEB card as the time grand master, communicating to a NTP server, and that it had a dedicated L61 to operate as the local time master for the rack, which then bridged to 2 different subnets using 2 different EN2Ts. All of the Logix PLCs were on those subnets.
IT's Network design has dictated that former time server rack is only connected to 1 VLAN. And now there are 4 VLANS in the Control Domain, one per Cisco Switch stack. When the time master moved to 1 VLAN, we lost time sync to half the Logix. As we moved Logix to the other 2 VLANs, it got worse.
So this is not an IMMEDIATE-PANIC type of problem. It's more of a nagging, it-should-get-done type of problem.
It will likely not progress until I get to site sometime in mid January. I was hoping to get something done this last week before Xmas .. but it didn't happen.