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