1) 通过mii-tool指令
       [root@localhost root]# mii-tool
        eth0: negotiated 100baseTx-FD, link ok
        eth1: no link
       或
       [root@localhost root]# mii-tool -v
        eth0: negotiated 100baseTx-FD, link ok
          product info: vendor 00:50:43, model 2 rev 3
          basic mode:   autonegotiation enabled
          basic status: autonegotiation complete, link ok
          capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
          advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control
          link partner: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
        eth1: no link
          product info: vendor 00:50:43, model 2 rev 3
          basic mode:   autonegotiation enabled
          basic status: no link
          capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
          advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control
       或
      [root@localhost root]# mii-tool -w
       21:20:33 eth0: negotiated 100baseTx-FD, link ok
       21:20:33 eth1: no link

      //mii-tool主要是用于配置网卡工作模式的指令，同时也可以进行查询、监控等工作！

  
   2)
     [root@localhost /]# /etc/init.d/network status
      Configured devices:
      lo eth0 eth1
      Currently active devices:
      lo eth0
     等同于
     [root@localhost root]# service --status-all
      ............
      ............
      Configured devices:
      lo eth0 eth1
      Currently active devices:
      lo eth0
      ............
      ............
   3)ifconfig -a
    [root@localhost /]# ifconfig -a
    eth0 Link encap:Ethernet HWaddr 00:09:6B:09:08:FC
          inet addr:192.168.10.1 Bcast:192.168.10.255 Mask:255.255.255.0
          inet6 addr: fe80::209:6bff:fe09:8fc/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:106732953 errors:0 dropped:0 overruns:0 frame:0
          TX packets:104379788 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:2351331877 (2.1 GiB) TX bytes:391707945 (373.5 MiB)
          Base address:0x2500 Memory:fbfe0000-fc000000
   eth1   Link encap:Ethernet HWaddr 00:09:6B:09:08:FD
          BROADCAST MULTICAST MTU:1500 Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
          Base address:0x2540 Memory:fbfc0000-fbfe0000

4)ethtool

#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: Full
        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

#ethtool eth1

Settings for eth1:
        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: Unknown! (0)
        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: no
从上面可以看出eth0 处于连接状态，eth1没有连接