ifconfig命令用来配置网络接口。
1. ifconfig默认会显示已经active的网络接口，
sh-# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0C:E7:06:00:00
          UP 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)
          Interrupt:40 Base address:0x2000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:1244 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1244 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:94792 (92.5 Kb)  TX bytes:94792 (92.5 Kb)

sh-#

2. ifconfig也可以查看指定网卡的信息，
sh-# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:0C:E7:06:00:00
          UP 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)
          Interrupt:40 Base address:0x2000

sh-#

3. 使用ifconfig命令修改IP地址，
sh-# ifconfig eth0 192.168.0.111 netmask 255.255.255.0
sh-#
sh-# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:0C:E7:06:00:00
          inet addr:192.168.0.111  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:92 errors:0 dropped:59 overruns:0 frame:0
          TX packets:42 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:11155 (10.8 Kb)  TX bytes:5318 (5.1 Kb)
          Interrupt:40 Base address:0x2000

sh-#

sh-# ifconfig eth0:0 192.168.0.112 netmask 255.255.255.0
sh-#

4. 使用ifconfig配置一块新的网卡eth0:0，但是发现配置之后ping不通了，
sh-#
sh-# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0C:E7:06:00:00
          inet addr:192.168.0.111  Bcast:192.168.0.255  Mask:255.255.255.0