https://www.peterpap.net/index.php?action=history&feed=atom&title=Forcing_Full_Duplex_on_CentOS%2FRedhat 2026-05-05T01:39:54Z Revision history for this page on the wiki MediaWiki 1.27.1 https://www.peterpap.net/index.php?title=Forcing_Full_Duplex_on_CentOS/Redhat&diff=25&oldid=prev 2010-09-20T06:12:09Z

<p>Created page with &quot;===== Forcing Full Duplex on CentOS/RedHat Linux ===== As with Solaris, if the network switch a CentOS/RedHat server is attached to is set to force 100mb full-duplex, the defaul...&quot;</p> <p><b>New page</b></p><div>===== Forcing Full Duplex on CentOS/RedHat Linux =====<br /> <br /> As with Solaris, if the network switch a CentOS/RedHat server is attached to is set to force 100mb full-duplex, the default behaviour of the server will be to autonegotiate to 100mb half-duplex. To change this, you can alter the running system with the 'ethtool' command. The 'ethtool' command can be used in the following ways:<br /> <br /> 1. To determine the current status of network interface 'eth0'<br /> <br /> [root@centos ~]# ethtool eth0<br /> Settings for eth0:<br /> Supported ports: [ MII ]<br /> Supported link modes: 10baseT/Half 10baseT/Full<br /> 100baseT/Half 100baseT/Full<br /> 1000baseT/Half 1000baseT/Full<br /> Supports auto-negotiation: Yes<br /> Advertised link modes: 10baseT/Half 10baseT/Full<br /> 100baseT/Half 100baseT/Full<br /> 1000baseT/Half 1000baseT/Full<br /> Advertised auto-negotiation: Yes<br /> Speed: 100Mb/s<br /> Duplex: Half<br /> Port: Twisted Pair<br /> PHYAD: 1<br /> Transceiver: internal<br /> Auto-negotiation: on<br /> Supports Wake-on: g<br /> Wake-on: d<br /> Current message level: 0x000000ff (255)<br /> Link detected: yes<br /> <br /> 2. To force 100mb full duplex and turn off autonegotiation on network interface 'eth0'<br /> <br /> [root@centos ~]# ethtool -s eth0 speed 100 duplex full autoneg off<br /> <br /> The output of the 'ethtool eth0' should now look like this:<br /> <br /> [root@centos ~]# ethtool eth0<br /> Settings for eth0:<br /> Supported ports: [ MII ]<br /> Supported link modes: 10baseT/Half 10baseT/Full<br /> 100baseT/Half 100baseT/Full<br /> 1000baseT/Half 1000baseT/Full<br /> Supports auto-negotiation: Yes<br /> Advertised link modes: Not reported<br /> Advertised auto-negotiation: No<br /> Speed: 100Mb/s<br /> Duplex: Full<br /> Port: Twisted Pair<br /> PHYAD: 1<br /> Transceiver: internal<br /> Auto-negotiation: off<br /> Supports Wake-on: g<br /> Wake-on: d<br /> Current message level: 0x000000ff (255)<br /> Link detected: yes<br /> <br /> '''NOTE:''' This change will be lost on the next reboot. <br /> <br /> 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:<br /> <br /> ETHTOOL_OPTS=&quot;speed 100 duplex full autoneg off&quot;</div>

Ppapa