How to force link speed to full-duplex

This article explains how to manually force the connection parameters for hosts to full-duplex operation on Debian, Ubuntu, CentOS and Windows 2012 or 2016 operating systems.

In our data centres, where Netgear switches are used, host switch port connections are forced to 100 Mbps full-duplex. Since all hosts by default attempt to auto-negotiate connection parameters, the host link defaults to 100 Mbps half-duplex as per the IEEE 802.3 standard. The connection parameters for all hosts that are set to run at half-duplex must be manually forced to achieve full-duplex operation.

  • For Linux servers please ensure that the tool called “ethtool” is installed on your OS. ethtool is used for querying settings of an ethernet device and changing them.

Debian and Ubuntu

In console run the following as root user:

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Insert last line as indicated on the image below

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Remember to use the actual interface name. You can check by running ‘ip link show’


In console run the following as root user:

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Insert last line as indicated on the image below.

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Windows Server 2012 R2, 2016 or 2019

Go to the Network adapters under Device Manager as follows:

  • Click on the Start button.
  • Right-click on Computer and select Manage.
  • Open Device Manager under Diagnostic and double click on Network adapters.
  • Double click on the correct adapter and select the Link Speed tab.
  • Select 100Mbps Full-Duplex under the Speed and Duplex dropdown box and click on OK.
  • Reboot server, log in again and confirm that the Link Speed is 100Mbps Full Duplex.

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