Cisco Catalyst 3750 Hardware Installation Manual page 146

Diagnosing Problems
Table 4-1 Common Problems and Solutions (continued)
Symptom
No connectivity
Catalyst 3750 Switch Hardware Installation Guide
4-6
Possible Cause
Incorrect or bad cable
These are results of no link at both
ends:
A crossover cable was used
•
when a straight-through was
required, or vice-versa.
The cable is wired incorrectly.
•
A crossover or straight-through
•
cable is wired incorrectly.
STP checking for possible
•
loops.
Chapter 4 Troubleshooting
Resolution
For the correct pinouts and
•
the proper application of
crossover vs.
straight-through cables, see
the "Two Twisted-Pair
Cable Pinouts" section on
page B-5.
• Enable the automatic
medium-dependent-
interface crossover
(Auto-MDIX) feature.
Many legacy powered
Note
devices, including older
Cisco IP phones and
access points that do not
fully support IEEE
802.3af, might not
support PoE when
connected to the
switches by a crossover
cable.
Replace with a tested good
•
cable.
For 1000BASE-T
•
connections, be sure to use
a twisted four-pair,
Category 5 cable.
Wait 30 seconds for the port
•
LED to turn green.
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