I configured my CenTOS server to use full duplex. I did this by editing the network script:
more /etc/sysconfig/network-scripts/ifcfg-eth0 DEVICE=eth0 ONBOOT=yes BOOTPROTO=static IPADDR=192.168.1.200 NETMASK=255.255.255.0 HWADDR=00:14:5E:0C:8B:E3 ETHTOOL_OPTS="speed 100 duplex full autoneg off"
(IPs and MAC has been renamed to protect the innocent =) )
After making this change, I ran service network restart
If I run mii-tool, i see:
eth0: no autonegotiation, 100baseTx-HD, link ok
However if I run ethtool eth0, I see:
Settings for eth0: Supported ports: [ TP ] 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: g Current message level: 0x000000ff (255) Link detected: yes
Why is there a discrepancy in the duplex? Mii-tool thinks that it's half and ethtool thinks that it's full.
Is ethtool not actually querying the current duplex state?