Cisco Catalyst 2955 Series User manual

CHAPTER
5-1
Catalyst 2955 Hardware Installation Guide
78-14944-03
5
Troubleshooting
The front-panel LEDs provide troubleshooting information about the switch.
They show power-on self-test (POST) failures, port-connectivity problems, and
overall switch performance. For a full description of the LEDs, see the “LEDs”
section on page 2-10.
You can also get statistics from the browser interface, the command-line interface
(CLI), the Cisco Intelligence Engine 2100 (IE2100) Series Configuration
Registrar, or a Simple Network Management Protocol (SNMP) workstation. See
the switch software configuration guide, the switch command reference, or the
documentation that came with your IE2100 or SNMP application for details.
This chapter provides these topics for troubleshooting problems:
•Understanding POST Results, page 5-2
•Diagnosing Problems, page 5-3

Chapter 5 Troubleshooting
Understanding POST Results
5-2
Catalyst 2955 Hardware Installation Guide 78-14944-03
Understanding POST Results
After the power is connected, the switch automatically begins POST, a series of
tests that verifies that the switch functions properly.
Note The uplink port status LEDs provide system and status information during POST.
On the Catalyst 2955C-12 and 2955S-12, the uplink ports are labeled 13 and 14.
On the Catalyst 2955T-12, the uplink ports are labeled 1 and 2.
Warning If you connect or disconnect the console cable with power applied to the
switch or any device on the network, an electrical arc can occur. This could
cause an explosion in hazardous location installations. Be sure that power is
removed or the area is nonhazardous before proceeding.
To verify switch operation, perform POST on the switch in a nonhazardous
location before installation. Statement 1065
When the Catalyst 2955C-12 and 2955S-12 begin POST:
•Uplink port 13 LED is amber.
•Uplink port 14 LED blinks green.
When the Catalyst 2955T-12 begins POST:
•Uplink port 1 LED is amber.
•Uplink port 2 LED blinks green.
If POST completes successfully on the Catalyst 2955C-12 and 2955S-12:
•Uplink port 13 LED turns green.
•Uplink port 14 LED goes off during the flash file system initialization.
If POST completes successfully on the Catalyst 2955T-12:
•Uplink port 1 LED turns green.
•Uplink port 2 LED goes off during the flash file system initialization.

5-3
Catalyst 2955 Hardware Installation Guide
78-14944-03
Chapter 5 Troubleshooting Diagnosing Problems
If POST fails on the Catalyst 2955C-12 and 2955S-12:
•Uplink port 13 LED blinks amber.
•Uplink port 14 LED turns green.
If POST fails on the Catalyst 2955T-12:
•Uplink port 1 LED blinks amber.
•Uplink port 2 LED turns green.
Note The uplink port status LEDs provide system and status information during POST.
On the Catalyst 2955T-12, the uplink ports are labeled 1 and 2. On the
Catalyst 2955C-12 and 2955S-12, the uplink ports are labeled 13 and 14.
POST failures are usually fatal. Call Cisco Systems immediately if your switch
does not pass POST. See the “Obtaining Technical Assistance” section on
page xxx.
Diagnosing Problems
Common switch problems fall into these categories:
•Poor performance
•No connectivity
•Corrupted software

Chapter 5 Troubleshooting
Diagnosing Problems
5-4
Catalyst 2955 Hardware Installation Guide 78-14944-03
Table 5-1 describes how to detect and solve these problems.
.
Table 5-1 Common Problems and Solutions
Symptom Possible Cause Resolution
Poor performance or
excessive errors. Duplex autonegotiation mismatch. See the switch software configuration guide for
information about identifying
autonegotiation mismatches.
Cabling distance exceeded.
•Port statistics show excessive
frame check sequence (FCS),
late-collision, or alignment
errors.
•See the switch software
configuration guide for
information about
displaying port statistics.
•For 10BASE-T, 100BASE-TX,
and 1000BASE-T connections:
– The distance between the
port and the attached device
exceeds 328 feet
(100 meters).
•Reduce cable length to
within the recommended
distances.
•For 100 and 1000 speed
connections:
– Wrong cable type (not
Cat 5) attached to device
and switch
•Replace wrong cable type
with Cat 5 cable.
– If the switch is attached to a
repeater, the total distance
between the two end
stations exceeds the cabling
guidelines.
•See your repeater
documentation for cabling
guidelines.
Bad adapter in attached device.
•Excessive errors found in port
statistics. •Run adapter card diagnostic utility.
Spanning Tree Protocol (STP)
checking for possible loops. Wait 30 seconds for port status LED to turn green.

5-5
Catalyst 2955 Hardware Installation Guide
78-14944-03
Chapter 5 Troubleshooting Diagnosing Problems
No connectivity. Incorrect or bad cable.
No link at both ends.
•A crossover cable was used
when a straight-through was
required, or vice-versa.
•For the correct pinouts and
the proper application of
crossover vs.
straight-through cables, see
the “Cable and Adapter
Specifications” section on
page B-5.
•The cable is wired incorrectly. •Replace it with a tested
good cable.
•STP checking for possible
loops. •Wait 30 seconds for port status LED to turn green.
Unreadable characters on
the management console. Incorrect baud rate. Reset the terminal-emulation software to 9600 baud.
System LED (Uplink port
status 13 LED) is amber,
and all port LEDs are off.
Corrupted software. Attach a monitor to the serial
port to display the switch boot
loader. For more information,
see the switch software
configuration guide.
System LED (Uplink port
13 LED) is amber. •Fatal POST error detected. •Contact Cisco Systems.
Table 5-1 Common Problems and Solutions (continued)
Symptom Possible Cause Resolution

Chapter 5 Troubleshooting
Diagnosing Problems
5-6
Catalyst 2955 Hardware Installation Guide 78-14944-03