3Figure 1 Speed auto negotiation application scenarioAs shown in Figure 1, the network card speed of each server in the server cluster (Server 1, Server 2, andServer 3) is 1000 Mbps, and the speed of GigabitEthernet 1/0/4, which provides access to the externalnetwork for the server group, is 1000 Mbps too. If you do not specify speed options for auto negotiationon the switch, the total rate of GigabitEthernet 1/0/1, GigabitEthernet 1/0/2 and GigabitEthernet1/0/3 will exceed 1000 Mbps, which may cause congestion on the egress interface GigabitEthernet1/0/4. To solve the problem, you can set 100 Mbps as the only option available for speed negotiationon GigabitEthernet 1/0/1, GigabitEthernet 1/0/2, and GigabitEthernet 1/0/3.Follow these steps to set speed options for auto negotiation on an Ethernet interface:To do… Use the command… RemarksEnter system view system-view —Enter Ethernet interface view interface interface-typeinterface-number —Configure the auto-negotiationtransmission rate range speed auto { 10 | 100 | 1000 } *OptionalThe auto-negotiation transmissionrate range is 10, 100, and 1000by default.NOTE:• This function is only available for Gigabit Layer-2 copper (electrical) Ethernet interfaces that supportspeed auto negotiation.• The speed and speed auto commands supersede each other, and whichever is configured last takeseffect.Configuring flow control on an Ethernet interfaceWhen flow control is enabled on both sides, if traffic congestion occurs at the ingress interface, it willsend a Pause frame notifying the egress interface to temporarily suspend the sending of packets. Theegress interface is expected to stop sending any new packet when it receives the Pause frame. In this way,flow control helps to avoid dropping of packets. Note that this will be possible only after flow control isenabled on both the ingress and egress interfaces.GE1/0/1GE1/0/2GE1/0/3
