MR46E high CRC errors and disconnects

[SteveLandon]

MR46E

Firmware:  MR30.5

Connected to MS120-8 FP  port 5  Trunk

The Problem is intermittent high crc errors on the MR46e.
The MR46e then disconnects. Cycling the port on the switch restores the MR46e.
Not much load the the MR - only 4 clients.
Cable tests have been run several times and it always shows clean. Cable length 120 ft CAT 6.
We've tried moving the MR46e to another port - same result. Very random and we have not been able to
pinpoint a problem. Logs show only many RSTP transitions on that port 5 of the switch.

SAMPLE LOG:
Jan 30 21:55:09 Port RSTP role change
Port 5 disabled→designated
Jan 30 21:55:09 Port status change
port: 5, old: down, new: 1Gfdx
Jan 30 21:55:07 Port RSTP role change
Port 5 designated→disabled
Jan 30 21:55:07 Port status change
port: 5, old: 1Gfdx, new: down

Any ideas are welcome.

[alemabrahao · Accepted solution]

CRC means physical problem, try replacing the cables to connect to another port.

[SteveLandon]

Cable or connector is what I thought too. The cable test always shows clean and we moved the connection to another port - same intermittent problem. Cable is difficult to get too but it looks like I'll have to replace it.

[BlakeRichardson]

Are you using structured cabling or just a single patch lead?  The built in cable tests are only some what informative. They only report issues with how the pairs are terminated and not the quality of the wires within the cable.

Something like a Fluke tester which costs thousands is the best approach for cable testing although the quick cheap fix is usually swapping patch leads. 

[SteveLandon]

It was intermittent and clear for now. It's a 90 meter cable and hard to get to. I've scheduled haveing the ends changed and see if that fixes it. Thanks for your suggestions.