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Configuration Guide - Interface Management

S1720, S2700, S5700, and S6720 V200R010C00

This document describes the principles and configurations of interfaces and provides configuration examples.

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Configuring Auto-Negotiation

Configuring Auto-Negotiation


Devices with different transmission capabilities exist on the network. Two devices must negotiate a proper data transmission capability to communicate. The auto-negotiation function provides an information exchange method for connected devices. After auto-negotiation is enabled, devices at both ends of a physical link can exchange information and automatically choose the same working parameters. In this way, the two devices can work at the maximum rate supported by both of them.

The duplex mode and rate of interfaces at both ends of a link are negotiated. 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. You can configure the connected interfaces to work in non-auto-negotiation mode, and forcibly set the same rate and duplex mode on the interfaces.

When the working mode of an interface is changed from auto-negotiation to non-auto-negotiation, the interface works at the maximum rate and uses the default duplex mode. For example, when a GE electrical interface works in auto-negotiation mode, the rate negotiated with the remote interface is 100 Mbit/s and the duplex mode is half-duplex. When the GE electrical interface is configured to work in non-auto-negotiation mode, the interface rate is restored to 1000 Mbit/s and the duplex mode is full-duplex.

  • For details about Ethernet interfaces supporting the auto-negotiation function, see Licensing Requirements and Limitations for Ethernet Interfaces.
  • 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 configuring the auto-negotiation function on an interface, if you remove and install a single optical fiber on the interface, the interface may be Up and the remote interface may be Down. You can run the shutdown and undo shutdown commands on the remote interface to make the remote interface go Up.
  • Interfaces at both ends of a link must use the same auto-negotiation mode. If they use different auto-negotiation modes, for example, the local end works in non-auto-negotiation mode and the remote end works in auto-negotiation mode, the local interface may be Up or Down, but the remote interface is always Down. As a result, the local and remote interfaces cannot communicate with each other.


  1. Run:


    The system view is displayed.

  2. Run:

    interface interface-type interface-number

    The interface view is displayed.

  3. Run:

    negotiation auto

    The Ethernet interface is configured to work in auto-negotiation mode.

    By default, an Ethernet interface works in auto-negotiation mode.

Checking the Configuration

Run the display interface [ interface-type [ interface-number ] ] command in any view or the display this interface command in the interface view to check the current interface status. Check the Negotiation field in the command output.

Updated: 2019-12-28

Document ID: EDOC1000141936

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