用ifconfig看网卡信息，有些信息查看不了，比如网卡上连线物理状态等信息。下边几个命令可以简单查看link信息：

1)

# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether d4:85:64:45:28:54 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether d4:85:64:45:28:55 brd ff:ff:ff:ff:ff:ff

2)

# ethtool eth0 | grep Link
	Link detected: yes

ethtool eth0是可以显示出所有跟eth0网卡相关的信息，比如速率等信息，
此处单独搜索Link状态

3)

# dmesg | grep eth
igb: eth0 NIC Link is Up 100 Mbps Full Duplex, Flow Control: RX/TX
igb: eth1 NIC Link is Up 100 Mbps Full Duplex, Flow Control: RX/TX
此处显示信息过多，单独抽取这两行说明

4)

# cat /sys/class/net/eth0/operstate 
up

5)

# mii-tool -h
mii-tool: invalid option -- 'h'
usage: mii-tool [-VvRrwl] [-A media,... | -F media] <interface> ...
       -V, --version               display version information
       -v, --verbose               more verbose output
       -R, --reset                 reset MII to poweron state
       -r, --restart               restart autonegotiation
       -w, --watch                 monitor for link status changes
       -l, --log                   with -w, write events to syslog
       -A, --advertise=media,...   advertise only specified media
       -F, --force=media           force specified media technology
media: 100baseT4, 100baseTx-FD, 100baseTx-HD, 10baseT-FD, 10baseT-HD,
       (to advertise both HD and FD) 100baseTx, 10baseT

mii-tool参数就这几个，自己添加使用就行。如：mii-tool -w eth0