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31-14
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
Chapter 31 Troubleshooting
GBIC and SFP Module Security and Identification
Note If a remote device does not autonegotiate, configure the duplex settings on the two ports to match. The
speed parameter can adjust itself even if the connected port does not autonegotiate.
GBIC and SFP Module Security and Identification
Cisco Course Wave Division Multiplexer (CWDM) Gigabit Interface Converter (GBIC) and small
form-factor pluggable (SFP) modules have a serial EEPROM that contains the module serial number, the
vendor name and ID, a unique security code, and cyclic redundancy check (CRC). When an CWDM
GBIC or SFP module is inserted in the switch, the switch software reads the EEPROM to check the serial
number, vendor name and vendor ID, and recompute the security code and CRC. If the serial number,
the vendor name or vendor ID, the security code, or CRC is invalid, the switch places the interface in an
error-disabled state.
Note If you are using a non-Cisco CWDM GBIC or SFP module, remove the GBIC or SFP module from the
switch, and replace it with a Cisco module.
After inserting a Cisco or module, use the errdisable recovery cause gbic-invalid global configuration
command to verify the port status, and enter a time interval for recovering from the error-disabled state.
After the elapsed interval, the switch brings the interface out of the error-disabled state and retries the
operation. For more information about the errdisable recovery command, see the command reference
for this release.
Diagnosing Connectivity Problems
This section describes how to troubleshoot connectivity problems:
• Using Ping, page 31-14
• Using Layer 2 Traceroute, page 31-16
Using Ping
This section consists of this information:
• Understanding Ping, page 31-14
• Executing Ping, page 31-15
Understanding Ping
The switch supports IP ping, which you can use to test connectivity to remote hosts. Ping sends an echo
request packet to an address and waits for a reply. Ping returns one of these responses:
• Normal response—The normal response (hostname is alive) occurs in 1 to 10 seconds, depending
on network traffic.
• Destination does not respond—If the host does not respond, a no-answer message is returned.
• Unknown host—If the host does not exist, an unknown host message is returned.