Cisco 3560G 48TS Software Configuration Guide - Page 790

Preventing Autonegotiation Mismatches Chapter 35 Troubleshooting Preventing Autonegotiation Mismatches The IEEE 802.3AB autonegotiation protocol manages the switch settings for speed (10 Mbps, 100 Mbps, and 1000 Mbps, excluding SFP module ports) 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. Troubleshooting Power over Ethernet Switch Ports If a powered device (such as a Cisco IP Phone 7910) that is connected to a PoE switch port and is being powered by an AC power source loses power from the AC power source, the device might enter an error-disabled state. To recover from an error-disabled state, enter the shut interface configuration command, and then enter the noshut interface command. Use these commands, described in the command reference for this release, to monitor PoE port status: • show controllers power inline privileged EXEC command • show power inline privileged EXEC command • debug ilpower privileged EXEC command SFP Module Security and Identification Cisco-approved 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 verify 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 software generates a security error message and places the interface in an error-disabled state. Note The security error message references the GBIC_SECURITY facility. The Catalyst 3560 switch supports SFP modules and does not support GBIC modules. Although the error message text refers to GBIC interfaces and modules, the security messages actually refer to the SFP modules and module interfaces. For more information about error messages, refer to the system message guide for this release. 35-12 Catalyst 3560 Switch Software Configuration Guide 78-16156-01