3Com 3CRUS2475 Command Reference Manual page 518

518 C 37: T
HAPTER ROUBLESHOOTING
Problem
No connection and the
port LED is off
Possible Cause
Incorrect ethernet cable,
e.g., crossed rather than
straight cable, or vice
versa, split pair (incorrect
twisting of pairs).
Fiber optical cable
connection is reversed.
Bad cable.
Wrong cable type.
Solution
Check pinout and
replace if necessary.
Change if necessary.
Check Rx and Tx on the
fiber-optic cable.
Replace with a tested
cable.
Verify that all 10 Mbps
connections use a Cat 5
cable.
Check the port LED or
zoom screen in the NMS
application, and change
settings if necessary.