Either the Ethernet cable is not plugged well in, or there is no power to the port. It could also show that the connection might be broken along the wire or a sign of a bad Ethernet port. The LED light on an Ethernet port appears to indicate the following: The speed of the connection. All these. It took me a further 5 months of complaining / sending photos of the meters for them to send someone out who instantly diagnosed the issue as being the communications hub which was flashing a red light on the WAN. msc, and click OK to open Device Manager. Are the LEDs on the PLC's Ethernet port showing normal link and activity status? To determine if the LEDs on a PLC's Ethernet port are showing normal link and activity status, refer to the standard Ethernet port LED behavior, which is generally as follows (though always confirm with the specific. Sometimes, you might find that only the power light is lit on your unmanaged switch when a DUT (device under test like a computer or a router) is connected to the switch, this problem might be caused by non-standard cable, the speed negotiation failure between the switch and the DUT, or the switch.
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