Extreme Networks ExtremeWare Version 7.8, Troubleshooting Manual

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Advanced System Diagnostics and Troubleshooting Guide 25
3
Packet Errors and Packet Error
Detection
This chapter describes some of the factors that might result in packet errors in the switch fabric and the
kinds of protection mechanisms that are applied to ensure that packet error events are minimized and
handled appropriately.
This chapter contains the following sections:
• Overview on page 25
• Definition of Terms on page 26
• Standard Ethernet Detection for Packet Errors on the Wire on page 27
•
Extreme Networks’ Complementary Detection of Packet Errors Between Wires on page 27
• Failure Modes on page 30
• Health Check Messages on page 33
Overview
Complex, wire-speed switch fabrics are subject to electronic anomalies that might result in packet errors.
The Ethernet standard contains built-in protections to detect packet errors on the link between devices,
but these mechanisms cannot always detect packet errors occurring in the switch fabric of a device.
Extreme Networks has incorporated many protection mechanisms to ensure that packet error events are
minimized and handled properly.
These protection mechanisms include the following:
• Ethernet CRC (detects packet errors between switches)
• Switch fabric checksums (automatic detection of live packet errors)
• Packet memory scanning (offline detection of packet memory errors)
• System health check (automatic test of various CPU and data paths)
• FDB scan (background scan process scans entire FDB RAM pool on all switch fabrics)
•
Transceiver check (background detects packet errors on internal control paths)