Hi All,
I have encountered odd issue, I was running tests on network cables connecting back to Cisco 9300-48P PoE switch. I was using Fluke LinkIQ network tester and occasionality I encountered message: "Unexpected Voltage, 3 SH 4.0 V"
If we break down the message, it states that there is voltage between Pin 3 and Shielding. I raised a case with Fluke and asked what this is all about as they have not documented this message in their manuals beyond statements, to not plug equipment into ISDN lines.
Fluke stated that it is possible that we have issues with mains power powering the network switches, something down the lines that there is some voltage traversing between Neutral and Earth wires. I followed their advise and determined that there are no issues I can see using multimeter:
Live(L), Earth(E) and Neutral(N), all looks ok,
L and E = 230V
L and N = 230V
E and N = 1V ( did search and found that up to two Volts it is acceptable in UK).
Then I took multimeter to actual Cat6A patch cord connecting to switch and I indeed am seeing around 4 Volts between Shield and Pin 3.
I had done test there I did go about disabling Power Inline on port, and still encountered same message. OI did tests on the same switch between different segments of ports and there were issues reported and then there were none reported, there were issues on one port which reported Unexpected Voltage at first and then subsequent tests did not show any issues.
Can someone please explain me what would be expected voltages between Ethernet Pins and shield, what could be causing this?
Worth to mention that these are switch stacks on some having 6x 9300-48P switches in it, all running IOS-XE 17.06.04, I do not recall seeing this issue before this version of software.
