Some times network connection in CentOS shows half duplex, there is a way to force it to full duplex.
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[root@centos ~]# ethtool eth0 Settings for eth0: Supported ports: [ MII ] Supported link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Half 1000baseT/Full Supports auto-negotiation: Yes Advertised link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Half 1000baseT/Full Advertised auto-negotiation: Yes Speed: 100Mb/s Duplex: Half Port: Twisted Pair PHYAD: 1 Transceiver: internal Auto-negotiation: on Supports Wake-on: g Wake-on: d Current message level: 0x000000ff (255) Link detected: yes |
To force 100mb full duplex and turn off autonegotiation on network interface ‘eth0’
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[root@centos ~]# ethtool -s eth0 speed 100 duplex full autoneg off |
The output of the ‘ethtool eth0’ should now look like this:
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[root@centos ~]# ethtool eth0 Settings for eth0: Supported ports: [ MII ] Supported link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Half 1000baseT/Full Supports auto-negotiation: Yes Advertised link modes: Not reported Advertised auto-negotiation: No Speed: 100Mb/s Duplex: Full Port: Twisted Pair PHYAD: 1 Transceiver: internal Auto-negotiation: off Supports Wake-on: g Wake-on: d Current message level: 0x000000ff (255) Link detected: yes |
NOTE: This change will be lost on the next reboot.
To make the change permanent, you need to edit the config file for the network interface. These live in /etc/sysconfig/network-scripts. Each interface will have a file called ‘ifcfg-ethX’, ie. for ‘eth0’ the file would be ‘ifcfg-eth0’. To make it so that when the machine is rebooted it comes up with the network interface at 100mb full-duplex, add the following line to this file:
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ETHTOOL_OPTS="speed 100 duplex full autoneg off" |
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