CPU 1516-3 PN/DP, TIA V17, six ET 200SP stations in a line. Last week we put a SCALANCE XB208 between the CPU's port 1 and the first station so a second Comfort panel could go close to the machine.
Everything runs. All six stations green, both panels online, no station failures. But since the switch went in, the MAINT LED on the CPU is yellow and won't clear, and the buffer says "Maintenance required. Neighbour mismatch, port 1. Configured partner: io-st1 port 1" or words to that effect. We put new patch cables on both sides of the switch, power cycled the CPU and the switch and downloaded the hardware again, and it comes back every time.
Is this the switch, or is a yellow MAINT LED just cosmetic? Not sure how hard to chase it. Could someone explain what the CPU is comparing when it says the neighbour on port 1 is the wrong one?
Did the integrator draw the port to port topology in the project, the topology view with lines between the ports? If he did, the CPU checks its neighbours over LLDP, and it might be seeing a switch where it expects io-st1.
Yes, the topology view was done fully, every port connected to the next station's port. The exact text now: "Neighbour mismatch on port 1. Expected: io-st1, port 1. Found: a different device." That's the whole entry.
That's it exactly. The topology in the project still says CPU port 1 to io-st1 port 1, and LLDP now tells the CPU its neighbour is the XB208. Not cosmetic, but not a fault either, it's the CPU telling you the drawing is wrong.
Two fixes. Drag the XB208 into the project from the catalog, put it in the topology view between the CPU and io-st1, connect the ports the way they're actually cabled, download. Or delete the port interconnections in the topology view and download, and the CPU stops checking, at the cost of device replacement without a card. I'd do the first one, the switch is part of the network now.
Added the XB208 to the project, drew it into the topology between CPU port 1 and io-st1 port 1, connected both ports, downloaded. MAINT LED off after a few seconds, buffer shows no new entry.
So the topology in the project still described the cabling from before the switch, and the CPU was telling me so in the only way it has. Drawing the XB208 in and downloading cleared it.
One thing I haven't done is give the XB208 a device name and IP in the project, it's still on its defaults and TIA warned about that. Will sort it next week. Thanks petek and dieter_k.
Yellow MAINT after someone adds a switch. We get that call twice a year.