Cisco 2950G 24 Software Configuration Guide - Page 575

Chapter 28 Troubleshooting GBIC and SFP Module Security and Identification Table 28-4 LRE Port Problems (continued) Problem High Reed-Solomon error count without CRC errors Ethernet performance degradation due to excessive network latency Suspected Cause and Suggested Solution • Interleaver is helping Reed-Solomon error correction to function correctly in a noisy environment. This situation means that the system is on the verge of generating CRC errors. - Change to a profile that has the interleaver feature enabled, such as the LRE-5, LRE-10, LRE-15, LRE-10-1, LRE-10-3, or LRE-10-5 profile. - Change to a profile with a lower data rate (for example, use LRE-5 instead of LRE-15) to increase the noise margin. • The LRE link length and quality are close to the limit of operation. - Change to a profile with a lower data rate (for example, use LRE-5 instead of LRE-15). - Reduce the effect of stubs or bridge taps by terminating them with 300-ohm microfilters. Interleaver introduces extra latency to increase noise margin. • Adjust upper-layer network protocols to allow for high latency. • Change to a profile with a higher data rate to increase link bandwidth. This decreases the noise margin. • Select a low-latency (LL) LRE profile, such as LRE-5LL, LRE-10LL, or LRE-15LL. Note Use the LL private profiles with care. The LL profiles have the LL feature enabled and the interleaver feature turned off. The LL feature does not delay data transmission, but it makes data more susceptible to interruptions on the LRE link. All other profiles, public and private, have the interleaver feature enabled and the LL feature disabled. The interleaver feature provides maximum protection against small interruptions on the LRE link but delays data transmission. For more information about the LRE profiles, see the "Types of LRE Profiles" section on page 7-17. LRE link quality Cross-talk between the LRE links is causing all links to degrade. Disable unused LRE ports by using reduced in installations the lre shutdown interface configuration command. with bundled cables GBIC and SFP Module Security and Identification Cisco-approved Gigabit Interface Converter (GBIC) 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 a GBIC 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 approved GBIC module, remove the GBIC from the switch, and replace it with a Cisco-approved module. After inserting a Cisco-approved GBIC or 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, refer to the command reference for this release. 78-14982-01 Catalyst 2950 Desktop Switch Software Configuration Guide 28-13