Cisco WS-C2950-24 Software Configuration Guide - Page 297
Avoiding Autonegotiation Mismatches
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Chapter 9 Troubleshooting Avoiding Autonegotiation Mismatches Avoiding Autonegotiation Mismatches The IEEE 802.3u autonegotiation protocol manages the switch settings for speed (10 Mbps or 100 Mbps) and duplex (half or full). Sometimes 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 Fast Ethernet 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. To connect to a remote Gigabit Ethernet device that does not autonegotiate, disable autonegotiation on the local device, and set the duplex and flow control parameters to be compatible with the remote device. 78-6511-05 Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide 9-3