Finding a duplex mismatch can be much more difficult than finding a speed mismatch, because if the duplex settings do not match on the ends of an Ethernet segment, the switch interface will still be in a connected (up/up) state. In this case, the interface works, but it might work poorly, with poor performance, and with symptoms of intermittent problems. The reason is that the device using half-duplex uses carrier sense multiple access collision detect (CSMA/CD) logic, waiting to send when receiving a frame, believing collisions occur when they physically do not—and actually stopping sending a frame because the switch thinks a collision occurred. With enough traffic load, the interface could be in a connect state, but i...
- Chapter 10. Troubleshooting Ethernet LANs
- from Cisco CCENT/CCNA ICND1 100-101 Official Cert Guide
- Publisher: Cisco Press
- Released: April 2013
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