Preventing autonegotiation mismatches, Sfp module security and identification, Diagnosing connectivity problems – IBM 12.1(22)EA6 User Manual
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Cisco Systems Intelligent Gigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide
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Chapter 25 Troubleshooting
Preventing Autonegotiation Mismatches
Preventing Autonegotiation Mismatches
The IEEE 802.3ab autonegotiation protocol manages the switch settings for speed (10 Mbps, 100 Mbps,
and 1000 Mbps) and duplex (half or full). There are situations when this protocol can incorrectly align
these settings, reducing performance. A mismatch occurs under these circumstances:
•
A manually set speed or duplex parameter is different from the manually set speed or duplex
parameter on the connected port.
•
A port is set to autonegotiate, and the connected port is set to full duplex with no autonegotiation.
To maximize switch performance and ensure a link, follow one of these guidelines when changing the
settings for duplex and speed:
•
Let both ports autonegotiate both speed and duplex.
•
Manually set the speed and duplex parameters for the ports on both ends of the connection.
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.
SFP Module Security and Identification
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
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 SFP module, remove the SFP module from the switch, and replace it with
a Cisco module.
After inserting a Cisco SFP 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:
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