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乙太網 Auto-Negotiation 和手動設定等連接組合的結果，從Cisco官網資訊整理
Posted: 08 Aug 2014 10:45 AM PDT
自動協商(Auto Negotiation) 是乙太網的一個很棒的功能，任何網路口接上線以後，我們不需要擔心任何速度(Speed)、雙工(Duplex)的設定內容，硬體自動就幫我們找到最好的設定。  | | EW線地鐵橋下的Upper Changi Road景觀。新加玻。 |
有趣的是，如果交換器端設定成手動，結果電腦端忘了做任何設定(預設是自動協商)，或者是兩者設定對調，結果竟然是速度很差的 半雙工！ | Configuration NIC (Speed/Duplex) | Configuration Switch (Speed/Duplex) | Resulting NIC Speed/Duplex | Resulting Catalyst Speed/Duplex | Comments |
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| AUTO | AUTO | 1000 Mbps, Full-duplex | 1000 Mbps, Full-duplex | Assuming maximum capability of Catalyst switch, and NIC is 1000 Mbps, full-duplex. | | 1000 Mbps, Full-duplex | AUTO | 1000 Mbps, Full-duplex | 1000 Mbps, Full-duplex | Link is established, but the switch does not see any autonegotiation information from NIC. Since Catalyst switches support only full-duplex operation with 1000 Mbps, they default to full-duplex, and this happens only when operating at 1000 Mbps. | | AUTO | 1000 Mbps, Full-duplex | 1000 Mbps, Full-duplex | 1000 Mbps, Full-duplex | Assuming maximum capability of NIC is 1000 Mbps, full-duplex. | | 1000 Mbps, Full-duplex | 1000 Mbps, Full-duplex | 1000 Mbps, Full-duplex | 1000 Mbps, Full-duplex | Correct Manual Configuration | | 100 Mbps, Full-duplex | 1000 Mbps, Full-duplex | No Link | No Link | Neither side establishes link, due to speed mismatch | | 100 Mbps, Full-duplex | AUTO | 100 Mbps, Full-duplex | 100 Mbps, Half-duplex | Duplex Mismatch 1 | | AUTO | 100 Mbps, Full-duplex | 100 Mbps, Half-duplex | 100 Mbps, Full-duplex | Duplex Mismatch 1 | | 100 Mbps, Full-duplex | 100 Mbps, Full-duplex | 100 Mbps, Full-duplex | 100 Mbps, Full-duplex | Correct Manual Configuration2 | | 100 Mbps, Half-duplex | AUTO | 100 Mbps, Half-duplex | 100 Mbps, Half-duplex | Link is established, but switch does not see any autonegotiation information from NIC and defaults to half-duplex when operating at 10/100 Mbps. | | 10 Mbps, Half-duplex | AUTO | 10 Mbps, Half-duplex | 10 Mbps, Half-duplex | Link is established, but switch does not see Fast Link Pulse (FLP) and defaults to 10 Mbps half-duplex. | | 10 Mbps, Half-duplex | 100 Mbps, Half-duplex | No Link | No Link | Neither side establishes link, due to speed mismatch. | | AUTO | 100 Mbps, Half-duplex | 100 Mbps, Half-duplex | 100 Mbps, Half-duplex | Link is established, but NIC does not see any autonegotiation information and defaults to 100 Mbps, half-duplex. | | AUTO | 10 Mbps, Half-duplex | 10 Mbps, Half-duplex | 10 Mbps, Half-duplex | Link is established, but NIC does not see FLP and defaults to 10 Mbps, half-duplex. |
其中，黃色代表最佳設定，橘色代表效能不好的設定，紅色代表完全不能使用的設定。
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