Overview
- Half-duplex mode: An interface in this mode can send data only when it is not receiving data and, conversely, it can receive data only when it is not sending data. A limit on the transmission distance applies to this mode.
- Full-duplex mode: An interface in this mode can send and receive data simultaneously. The maximum throughput in full-duplex mode is theoretically double that in half-duplex mode. There is no limit on the transmission distance in this mode.
- In auto-negotiation mode, interfaces at both ends of a link negotiate the rate and duplex mode. If the negotiation succeeds, the two interfaces use the same duplex mode and rate. The auto-negotiation function takes effect only when both the connected devices support it. If the remote device does not support auto-negotiation or uses a different auto-negotiation mode, the connected interfaces may be Down.
You can configure the local interface to work in non-auto-negotiation mode and manually configure the interface rate and duplex mode in the following situations:
The remote device does not support auto-negotiation.
After auto-negotiation is configured, the local and remote devices cannot communicate.
After auto-negotiation is configured, the physical link between the local and remote devices is connected, but many error packets are generated or packet loss occurs.
Configuration Notes
- Usage restrictions
Ethernet interfaces at both ends of a link must work in the same auto-negotiation mode. Otherwise, the interfaces may be Down.
When the working rate of a GE electrical interface is 1000 Mbit/s, the interface supports only the full-duplex mode and does not need to negotiate the duplex mode with the remote interface.
Interfaces at both ends of a link must use the same rate and duplex mode.
Rate and duplex mode of Ethernet interfaces lists the rate and duplex mode of Ethernet interfaces.
Networking Requirements
As shown in Figure 5-2, Server1, Server2, and Server3 form a server cluster and connect to GE1/0/1, GE1/0/2, and GE1/0/3 of the Switch respectively. The Switch connects to the Internet through GE1/0/4.
Due to limitations of network adapters on the servers, GE1/0/1, GE1/0/2, and GE1/0/3 can only work in half-duplex mode after negotiating with connected server interfaces. As a result, packet loss occurs when the service traffic volume is high. In addition, the rate is negotiated to 1000 Mbit/s for GE1/0/1, GE1/0/2, and GE1/0/3. When the three servers concurrently send data at the rate of 1000 Mbit/s, the outbound interface GE1/0/4 will be congested. Users require that packet loss and congestion do not occur.

Configuration Roadmap
The configuration roadmap is as follows:
- Configure the switch interfaces to work in non-auto-negotiation mode to prevent the interface rate from being affected by the network adapter rate on the servers.
Set the duplex mode to full-duplex for the interfaces working in non-auto-negotiation mode to avoid packet loss.
Set the rate to 100 Mbit/s for the interfaces working in non-auto-negotiation mode to avoid congestion on the outbound interface.
Procedure
- Create a port group and add GE1/0/1, GE1/0/2, and GE1/0/3 to the port group.
<HUAWEI> system-view[HUAWEI] sysname Switch[Switch] port-group portgroup1 //Create a permanent port group portgroup1.[Switch-port-group-portgroup1] group-member GE1/0/1 to GE1/0/3 //Add GE1/0/1,GE1/0/2, and GE1/0/3 to portgroup1.
- Configure GE1/0/1, GE1/0/2, and GE1/0/3to work in non-auto-negotiation mode, and set the duplex mode to full-duplex and rate to 100 Mbit/s for these interfaces in a batch.
[Switch-port-group-portgroup1] undo negotiation auto //Configure interfaces to work in non-auto-negotiation mode in a batch.[Switch-GigabitEthernet1/0/1] undo negotiation auto[Switch-GigabitEthernet1/0/2] undo negotiation auto[Switch-GigabitEthernet1/0/3] undo negotiation auto[Switch-port-group-portgroup1] duplex full //Set the duplex mode of the interfaces to full-duplex in a batch.[Switch-GigabitEthernet1/0/1] duplex full[Switch-GigabitEthernet1/0/2] duplex full[Switch-GigabitEthernet1/0/3] duplex full[Switch-port-group-portgroup1] speed 100 //Set the rate of the interfaces to 100 Mbit/s in a batch.[Switch-GigabitEthernet1/0/1] speed 100[Switch-GigabitEthernet1/0/2] speed 100[Switch-GigabitEthernet1/0/3] speed 100[Switch-port-group-portgroup1] quit
- Verify the configuration.
Run the display interface gigabitethernet 1/0/1 command in any view to check the interface rate and duplex mode.
[Switch] display interface gigabitethernet 1/0/1... Port Mode: COMMON COPPER Speed : 100, Loopback: NONE Duplex: FULL, Negotiation: DISABLE Mdi : AUTO, Flow-control: DISABLE ...
The command output shows that the interface works in non-negotiation mode, the rate is 100 Mbit/s, and the duplex mode is full-duplex.
Similarly, run the display interface gigabitethernet 1/0/2 and display interface gigabitethernet 1/0/3 commands on GE1/0/2 and GE1/0/3respectively to check interface working information.
Configuration File
Switch configuration file
# sysname Switch# interface GigabitEthernet1/0/1 undo negotiation auto speed 100 # interface GigabitEthernet1/0/2 undo negotiation auto speed 100 # interface GigabitEthernet1/0/3 undo negotiation auto speed 100 # port-group portgroup1 group-member GigabitEthernet1/0/1 group-member GigabitEthernet1/0/2 group-member GigabitEthernet1/0/3 # return
Rate and duplex mode of Ethernet interfaces
Interface Type | Rate and Duplex mode |
---|---|
MultiGE interfaces |
NOTE:
|
FE electrical interfaces |
|
GE electrical interfaces |
NOTE:
|
XGE (10GE) electrical interfaces |
NOTE: Only ES5D21X08T00 card of the S5730HI and ES5D21X02T01 card of the S5720EI support XGE electrical interfaces. |
FE optical interfaces |
|
GE optical interfaces | When the transmission medium is an FE optical module:
When the transmission medium is a GE optical module:
When the transmission medium is a GE copper module:
NOTE: By default, auto-negotiation is enabled on GE optical interfaces and rate auto-negotiation is disabled. You can run the speed auto-negotiation command to enable rate auto-negotiation. After a GE interface on the S5700SI, S5700EI, or S5700HI has a GE copper module installed, the interface can go Up. However, you cannot configure the rate, duplex mode, and auto-negotiation mode on the interface. |
XGE (10GE) optical interfaces | When the transmission medium is an XGE optical module:
When the transmission medium is a GE optical module:
When the transmission medium is a GE copper module:
When the transmission medium is an XGE/GE optical module:
NOTE:
|
40GE optical interfaces | When the transmission medium is a 40GE optical module
When the transmission medium is a high-speed cable:
NOTE: When you run the display interface command on a 40GE optical interface that has a high-speed cable installed, the command output shows that auto-negotiation is enabled. However, you cannot run the negotiation auto command to configure the auto-negotiation mode. |
100GE optical interfaces |
NOTE: Only the S6720HI supports 100GE optical interfaces. |
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