
Troubleshooting a Physical Media Problem
4-5
You can also loop back PPP lines. But if you configured them with a
password, you must configure them in promiscuous mode first.
If you are accessing a DTE/DCE line with promiscuous mode off, the port
will not increment the reception statistics.
If the connection is FDDI or ATM Rx and Tx,
a. Make sure you cabled correctly the A and B ports.
b. Try looping Port A back to Port B to test for port failure.
If the Tx and Rx LEDs light, the ports and cable are OK.
c. Check the event log to make sure that the router brings the ring up
and marks the circuit as active.
d. If the loopback test fails, try a different fiber cable. Then try
replacing the link module.
Note: Multimode fiber is orange, and single-mode fiber is yellow. The
different fibers require different interface modules.
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