ethtool使用记录

网卡出现很诡异的问题，把电脑连到一些交换机上是工作的，连到另外一些就不行。。。交换机上的link灯还时不时的闪一下，看起来像是在尝试连接。

用dmesg查看，看到下面的信息：

[ 1112.922110] jme 0000:05:00.5: irq 46 for MSI/MSI-X
[ 1112.944596] jme 0000:05:00.5: eth0: Link is down
[ 1112.945228] ADDRCONF(NETDEV_UP): eth0: link is not ready

查了半天，也没弄明白是怎么回事，有人说是驱动问题。另外看到有人推荐用ethtool来强制定义为100M以太网。方法如下

sudo ethtool -s eth0 speed 100 duplex full autoneg off

设置后的效果，可以使用sudo ethtool eth0来查看。比如，我设置之前是

Settings for eth0:
    Supported ports: [ TP MII ]
    Supported link modes:   10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Half 1000baseT/Full 
    Supported pause frame use: No
    Supports auto-negotiation: Yes
    Advertised link modes:  Not reported
    Advertised pause frame use: No
    Advertised auto-negotiation: No
    Speed: 100Mb/s
    Duplex: Full
    Port: MII
    PHYAD: 1
    Transceiver: internal
    Auto-negotiation: off
    Supports Wake-on: pg
    Wake-on: d
    Current message level: 0x000020c6 (8390)
                   probe link rx_err tx_err hw
    Link detected: no

设置之后是：

Settings for eth0:
    Supported ports: [ TP MII ]
    Supported link modes:   10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Half 1000baseT/Full 
    Supported pause frame use: No
    Supports auto-negotiation: Yes
    Advertised link modes:  Not reported
    Advertised pause frame use: No
    Advertised auto-negotiation: No
    Speed: 100Mb/s
    Duplex: Full
    Port: MII
    PHYAD: 1
    Transceiver: internal
    Auto-negotiation: off
    Supports Wake-on: pg
    Wake-on: d
    Current message level: 0x000020c6 (8390)
                   probe link rx_err tx_err hw
    Link detected: yes

其中，最后Link detected是表示是否已检测到有以太网连接的。。。说明强制100M之后，就连上了。。。

不知道这是为什么，反正100M也能适应大多是情况了，先暂且如此。