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How to fix "Internal Loopback Test Fail" on Baystack 350T

Rowan Hawkins
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Last Modified: 2010-08-05
We have a Baystack 350T 10/100 Autosense 16-port Switch.  We have a couple of questions about it.  Upon connecting to the console port we receive an error message stating the Port internal loopback test has failed. What is the cause of this error and is there a solution to fix this error without sending the hardware back to Nortel for service?
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Gennerally this means that one of the asic's has failed which is a hardware failure ... and must be repaired at nortel..... sorry
Rowan HawkinsSystem Integrator
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Commented:
the screen says that ASIC's have passed their addressing and buffer RAM tests, and the physical layer test passes as well.
Since it is a port loopback test that is failing, is it possible to exclude the port maybe?

I have surface mount rework experience.  but I dont know if it is an internal device port or a switch port that is causing the problem.  if it is external I might be able to get it working again.
Rowan HawkinsSystem Integrator
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I have increased the point value because the nature of the question has become harder.
What the error means is that during its self test it activated an internal loopback on one of its ports and sent test data to it but did not receive the test pattern back correctly.  As Scotty said, one of your asic's has failed.  Likely most of the ports on it still work and can still be used.  It just has at least one bad one.

-Pascal
Rowan HawkinsSystem Integrator
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Pascal,

    Yes I had come to that conclusion too. The problem is that the POST is not completing and I am unable to enter the management console.  I understand that the switch will work as a switch but I would like to disable the VLANs on it. which can only be done though management.  I am trying to figure out a way to get past the error.

   Interestingly enough, the circuitry on the board is quite modularized for each port. Though having a schematic would make my life much easier.  For each port, there is a couple of capacitors, a load, 4 transistors, a couple more capicitors and resistors and then what I think is the ASIC under a heat sink.  some more circuitry and  then you get to 0ne of 10 NetICS chips followed by a pair of TI controllers. the bottom is a mess of surface mount capicitors and resistors all sandwiched with a 6 layer board between. (does this sound fun yet?)

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Rowan HawkinsSystem Integrator
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hmm I didnt get a message with the administrative comment, otherwise I would have discontinued it myself.

I still have the item and it will be a project in the unlikely event that I have free time.

Thanks Guys/Gals
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