If the NetworkManager
service is running, you can use the
nm-tool command to display a verbose listing of the state of the system's
physical network interfaces, for example:
# nm-tool
NetworkManager Tool
State: connected
- Device: eth0 [System eth0] --------------------------------------------------
Type: Wired
Driver: e1000
State: connected
Default: yes
HW Address: 08:00:27:16:C3:33
Capabilities:
Carrier Detect: yes
Speed: 1000 Mb/s
Wired Properties
Carrier: on
IPv4 Settings:
Address: 10.0.2.15
Prefix: 24 (255.255.255.0)
Gateway: 10.0.2.2
DNS: 192.168.249.52
DNS: 192.168.249.41
You can also use the ip command to display the status of an interface, for debugging, or for system tuning. For example, to display the status of all active interfaces:
# ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 08:00:27:16:c3:33 brd ff:ff:ff:ff:ff:ff
inet 10.0.2.15/24 brd 10.0.2.255 scope global eth0
inet6 fe80::a00:27ff:fe16:c333/64 scope link
valid_lft forever preferred_lft forever
For each network interface, the output shows the current IP address, and the status of the
interface. To display the status of a single interface such as eth0
,
specify its name as shown here:
# ip addr show dev eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 08:00:27:16:c3:33 brd ff:ff:ff:ff:ff:ff
inet 10.0.2.15/24 brd 10.0.2.255 scope global eth0
inet6 fe80::a00:27ff:fe16:c333/64 scope link
valid_lft forever preferred_lft forever
You can also use ip to set properties and activate a network interface.
The following example sets the IP address of the eth1
interface and
activates it:
#ip addr add 10.1.1.1/24 dev eth1
#ip link set eth1 up
You might be used to using the ifconfig command to perform these operations. However, ifconfig is considered obsolete and will eventually be replaced altogether by the ip command.
Any settings that you configure for network interfaces using ip do not
persist across system reboots. To make the changes permanent, set the properties in the
/etc/sysconfig/network-scripts/ifcfg-
file.interface
Any changes that you make to an interface file in
/etc/sysconfig/network-scripts
do not take effect until you restart the
network service or bring the interface down and back up again. For example, to restart the
network service:
# service network restart
Shutting down interface eth0: Device state: 3 (disconnected)
[ OK ]
Shutting down loopback interface: [ OK ]
Bringing up loopback interface: [ OK ]
Bringing up interface eth0: Active connection state: activating
Active connection path: /org/freedesktop/NetworkManager/ActiveConnection/1
state: activated
Connection activated
[ OK ]
To restart an individual interface, you can use the ifup or
ifdown commands, which invoke the script in
/etc/sysconfig/network-scripts
that corresponds to the interface type,
for example:
#ifdown eth0
Device state: 3 (disconnected) #ifup eth0
Active connection state: activating Active connection path: /org/freedesktop/NetworkManager/ActiveConnection/1 state: activated Connection activated
Alternatively, you can use the ip command:
#ip link set eth0 down
#ip link set eth0 up
The ethtool utility is useful for diagnosing potentially mismatched
settings that affect performance, and allows you to query and set the low-level properties of
a network device. Any changes that you make using ethtool do not persist
across a reboot. To make the changes permanent, modify the settings in the device's
ifcfg-
file in
interface
/etc/sysconfig/network-scripts
.
For more information, see the ethtool(8)
, ifup(8)
,
ip(8)
, and nm-tool(1)
manual pages.