Learn to use ifconfig by
example
command 'ifconfig' is used to config a network interface.
Here we list a few cases that might be frequently used.
List the network interface information.
Our example machine is Dublin who has one
3com NIC card which is running, 2 DECchip tulip NIC cards which are not set well
yet.
1. without any option, any argument, ifconfig
lists only the interfaces that are working.
[root@dublin /root]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:B0:D0:D8:FE:09
inet addr:132.177.8.28 Bcast:132.177.8.127 Mask:255.255.255.128
inet6 addr: fe80::2b0:d0ff:fed8:fe09/10 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:45414 errors:0 dropped:0 overruns:0 frame:0
TX packets:7441 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
Interrupt:5 Base address:0xe880
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:6 errors:0 dropped:0 overruns:0 frame:0
TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
1.5 Apply "ifconfig" on one NIC interface will
display that interface info
[root@dublin /root]# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:B0:D0:D8:FE:09
inet addr:132.177.8.28 Bcast:132.177.8.127 Mask:255.255.255.128
inet6 addr: fe80::2b0:d0ff:fed8:fe09/10 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:46123 errors:0 dropped:0 overruns:0 frame:0
TX packets:7512 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
Interrupt:5 Base address:0xe880
2. with option -a, ifconfig lists all possible
network interfaces( including virtual interfaces ).
[root@dublin /root]# ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:B0:D0:D8:FE:09
inet addr:132.177.8.28 Bcast:132.177.8.127 Mask:255.255.255.128
inet6 addr: fe80::2b0:d0ff:fed8:fe09/10 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:45796 errors:0 dropped:0 overruns:0 frame:0
TX packets:7487 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
Interrupt:5 Base address:0xe880
eth1 Link encap:Ethernet HWaddr 00:C0:F0:6A:56:51
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:100
Interrupt:10 Base address:0x4c00
eth2 Link encap:Ethernet HWaddr 00:C0:F0:6A:6D:0C
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:100
Interrupt:11 Base address:0x6800
gre0 Link encap:UNSPEC HWaddr
00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
NOARP MTU:1476 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:0
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:6 errors:0 dropped:0 overruns:0 frame:0
TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
sit0 Link encap:IPv6-in-IPv4
NOARP MTU:1480 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:0
teql0 Link encap:UNSPEC HWaddr
00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
NOARP 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:100
tunl0 Link encap:IPIP Tunnel HWaddr
NOARP MTU:1480 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:0
The above command is running on latest kernel 2.4.10 which includes all
possible networking options. interfaces other than eth* are virtual interfaces.
Here we see that eth1 and eth2 are down.
You may need to insert the NIC card modules before you see eth1, eth2.
(login as root and use "insmod tulip" to install NIC driver to kernel )
3. To assign ip address for the Ethernet card
#ifconfig eth1 192.168.2.1 netmask 255.255.255.0 up
#ifconfig eth1
eth1 Link encap:Ethernet HWaddr 00:C0:F0:6A:56:51
inet addr:192.168.2.1 Bcast:192.168.2.255 Mask:255.255.255.0
inet6 addr: fe80::2c0:f0ff:fe6a:5651/10 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:1 dropped:0 overruns:0 frame:0
TX packets:0 errors:2 dropped:0 overruns:0 carrier:2
collisions:0 txqueuelen:100
Interrupt:10 Base address:0x4c00
IP address is set up and brought successfully
4. To disable on NIC interface
#ifconfig eth1 down
# ifconfig eth1
eth1 Link encap:Ethernet HWaddr 00:C0:F0:6A:56:51
inet addr:192.168.2.1 Bcast:192.168.2.255 Mask:255.255.255.0
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:1 dropped:0 overruns:0 frame:0
TX packets:2 errors:2 dropped:0 overruns:0 carrier:2
collisions:0 txqueuelen:100
Interrupt:10 Base address:0x4c00
4. To bring up a NIC interface
#ifconfig eth1 up
For more information on command "ifconfig", See man page