Linux下如何通过命令检查网卡是否插上网线

How To:Linux下如何通过命令检查网卡是否插上网线

 

主要工具为ethtool来检查，主要关注的字段为"Link detected"，注意如下的输出，其中em4实际物理上并未插上网线，而em1是插上网线的：

# ethtool em4
Settings for em4:
        Supported ports: [ TP ]
        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:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Half 1000baseT/Full
        Advertised pause frame use: Symmetric
        Advertised auto-negotiation: Yes
        Speed: Unknown!
        Duplex: Unknown! (255)
        Port: Twisted Pair
        PHYAD: 2
        Transceiver: internal
        Auto-negotiation: on
        MDI-X: Unknown
        Supports Wake-on: g
        Wake-on: d
        Current message level: 0x000000ff (255)
                               drv probe link timer ifdown ifup rx_err tx_err
        Link detected: no
# ethtool em1
Settings for em1:
        Supported ports: [ TP ]
        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:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Half 1000baseT/Full
        Advertised pause frame use: Symmetric
        Advertised auto-negotiation: Yes
        Link partner advertised link modes:  100baseT/Full
                                             1000baseT/Full
        Link partner advertised pause frame use: Transmit-only
        Link partner advertised auto-negotiation: Yes
        Speed: 1000Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        Auto-negotiation: on
        MDI-X: on
        Supports Wake-on: g
        Wake-on: d
        Current message level: 0x000000ff (255)
                               drv probe link timer ifdown ifup rx_err tx_err
        Link detected: yes

此外，还可以ifconfig 命令：

1.  首先让我们通过xshell登录一台linux服务器，查看一下当前这台机器有几块网卡：ifconfig -a;我们这台机器有两块网卡分别是eth0和eth1
2.  

   然后让我们模拟一下环境：拔掉eth1的网线，再次执行：ifconfig -a这条命令，对比一下eth0和eth1的区别，发现eht1不再running。没错这个字段就是看网卡是否有连线的，或者网线是否有问题的。

   
3.  

   接着让我们把eth1的网线插上，再执行一遍：ifconfig -a；对比一下eth0和eth1，发现此时eth1已经running了。