ethtool command is helpful to check the speed and change settings of network interface, also get information which works now for most network interface cards.
How to Install ethtool on Linux
Ubuntu / Debian:
# sudo apt-get install ethtool -y
CentOS / Red Hat Enterprise :
# yum install ethtool -y
Package Arch Version Repository Size
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ethtool x86_64 2:3.15-2.el7 base 113 k
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Installing : 2:ethtool-3.15-2.el7.x86_64
Verifying : 2:ethtool-3.15-2.el7.x86_64
To check the network interface of eth0 run,
# ethtool eth0
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Speed: 100Mb/s
Duplex: Half
Port: Twisted Pair
PHYAD: 2
Transceiver: internal
Auto-negotiation: on
MDI-X: on
Supports Wake-on: pumbg
Wake-on: g
Current message level: 0x00000007 (7)
Link detected: yes
Change the Network Speed to 100MBps full Duplex mode, run
# ethtool -s eth0 autoneg off speed 100 duplex full
Change the network speed to 1000Mbps, full duplex mode, run
# ethtool -s eth0 speed 1000 duplex full autoneg off
To make a speed change permanent for eth0, we need to set or add the ETHTOOL_OPT environment variable in network configuration file
# vim /etc/sysconfig/network-scripts/ifcfg-eth0
ETHTOOL_OPTS="speed 1000 duplex full autoneg off"
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