Chapter 34. Configuring 802.3 link settings
34.1. Understanding Auto-negotiation
Auto-negotiation is a feature of the IEEE 802.3u Fast Ethernet protocol. It targets the device ports to provide an optimal performance of speed, duplex mode, and flow control for information exchange over a link. Using the auto-negotiation protocol, you have optimal performance of data transfer over the Ethernet.
To utilize maximum performance of auto-negotiation, use the same configuration on both sides of a link.
34.2. Configuring 802.3 link settings using the nmcli utility
To configure the 802.3 link settings of an Ethernet connection, modify the following configuration parameters:
-
802-3-ethernet.auto-negotiate -
802-3-ethernet.speed -
802-3-ethernet.duplex
Procedure
Display the current settings of the connection:
# nmcli connection show Example-connection ... 802-3-ethernet.speed: 0 802-3-ethernet.duplex: -- 802-3-ethernet.auto-negotiate: no ...You can use these values if you need to reset the parameters in case of any problems.
Set the speed and duplex link settings:
# nmcli connection modify Example-connection 802-3-ethernet.auto-negotiate yes 802-3-ethernet.speed 10000 802-3-ethernet.duplex fullThis command enables auto-negotiation and sets the speed of the connection to
10000Mbit full duplex.Reactivate the connection:
# nmcli connection up Example-connection
Verification
Use the
ethtoolutility to verify the values of Ethernet interfaceenp1s0:# ethtool enp1s0 Settings for enp1s0: ... Speed: 10000 Mb/s Duplex: Full Auto-negotiation: on ... Link detected: yes
Additional resources
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nm-settings(5)man page