Bagging line. CompactLogix 1769 L33ER, Studio 5000 V33. Two 1734-AENTR racks, a PowerFlex 525 and a PanelView Plus 7, all hanging off a Stratix 5700 that IT manage now.
Last month IT did a security pass on the switch and the line's been slow ever since. HMI tags lag, the AENTR racks throw 16#0204 a couple of times a shift, and the drive dropped off twice yesterday.
IT say the port's fine. They set it to 100 full so nothing can negotiate down, and they sent me the show interface output with input errors and CRC counting up.
I've swapped in a new shielded cable on the controller port and moved the AENTRs onto other ports, no change at all. Is it the controller port itself? Or does 100 full fixed on their end want something set to match on mine, because I'm not sure where that would even be?
Is the CRC on the controller's port only, or on the AENTR ports as well? If it's only the one port I'd still be looking at that link. We had a cable pass a tester and still throw CRC on the press line, and it turned out to be the jack in the panel, not the lead.
Only the controller port. The AENTR ports are clean and IT checked every one of them. The jack I've already bypassed, straight lead from the L33ER port 1 to the switch, 3 m, no luck, still counts up. About 200 CRC an hour.
Clean everywhere except the port IT touched. Ask them for the full show interface output, the line that reads speed and duplex, and get the same off the controller side. Studio 5000, controller properties, Port Configuration, there's a Port Diagnostics button on it. Speed, duplex and the late collisions counter. Don't guess, read both ends.
Switch says Full-duplex, 100Mb/s, and a line saying duplex is not auto. Controller Port Diagnostics says link up, autonegotiation attempted but failed, 100 Mbps, half duplex. Late collisions 1,412 and climbing while I watched. So the two ends disagree. I've never set a thing on the L33, it's on auto.
That's a duplex mismatch. Autonegotiation is a conversation. IT forced their end, so their port stopped talking. Your controller still listens, hears nothing, and the standard says fall back to half duplex when the partner says nothing. Speed it can sense off the signal, duplex it can't. So the switch sends whenever it likes, the controller waits for a quiet line, and every overlap is a late collision on your side and a CRC on theirs.
Fix is both ends the same. Auto on both is what Rockwell recommend for these ports. If IT insist on fixed, fix the controller too, Port Configuration tab, untick auto-negotiate, 100 full. There's a writeup covering this here: https://plctr.com/advanced-plc-networking-and-communication-protocols/
IT put the port back to auto this morning. Controller Port Diagnostics now reads 100 full, negotiation successful. Late collisions stopped dead at 1,412 and the CRC on the switch stopped in the same minute. Shift ran, no 16#0204, HMI is quick again.
So it was a duplex mismatch after all. IT forced 100 full on their side, the 1769 L33ER fell back to half, and auto on both ends fixed it. They wanted it left fixed for their standard, I showed them the counters and they gave in.
What I still don't get is why it took a month to bite. Maybe it was always this bad and nobody was counting. Thanks suel, sparkymike.
Same standard bit our filler line. IT backed off after a week.