How to renew your network interface IP address on Linux with the dhclient command.

Posted: September 29, 2013. At: 9:10 PM. This was 4 years ago. Post ID: 6354
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The dhclient command on Linux is used to renew an IP address for a network interface. Here i am using Fedora 19 with the new standardised network interface names.

root@neo homer# dhclient -v wlp0s26f7u5
Internet Systems Consortium DHCP Client 4.2.5
Copyright 2004-2013 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
 
Listening on LPF/wlp0s26f7u5/e0:91:f5:23:fd:ad
Sending on   LPF/wlp0s26f7u5/e0:91:f5:23:fd:ad
Sending on   Socket/fallback
DHCPDISCOVER on wlp0s26f7u5 to 255.255.255.255 port 67 interval 4 (xid=0x3791798e)
DHCPREQUEST on wlp0s26f7u5 to 255.255.255.255 port 67 (xid=0x3791798e)
DHCPOFFER from 192.168.1.1
DHCPACK from 192.168.1.1 (xid=0x3791798e)
bound to 192.168.1.3 -- renewal in 41575 seconds.

This command will attempt to set a new IP address for your network adapter.

Here is another example of the usage of this command.

Stopping the network interface.

[email protected]:~$ sudo dhclient -r
avahi-daemon start/running, process 2643

Checking that we have no IP address now.

[email protected]:~$ ifconfig 
eth0      Link encap:Ethernet  HWaddr 08:00:27:85:68:81  
          inet6 addr: fe80::a00:27ff:fe85:6881/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:52 errors:0 dropped:0 overruns:0 frame:0
          TX packets:93 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:6987 (6.9 KB)  TX bytes:12712 (12.7 KB)
          Interrupt:19 Base address:0xd000 
 
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:65536  Metric:1
          RX packets:12 errors:0 dropped:0 overruns:0 frame:0
          TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:868 (868.0 B)  TX bytes:868 (868.0 B)

Bringing the network interface back up.

[email protected]:~$ sudo dhclient eth0
avahi-daemon stop/waiting

And checking the IP address again gives us what we want.

[email protected]:~$ ifconfig 
eth0      Link encap:Ethernet  HWaddr 08:00:27:85:68:81  
          inet addr:192.168.1.7  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fe85:6881/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:58 errors:0 dropped:0 overruns:0 frame:0
          TX packets:105 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:8093 (8.0 KB)  TX bytes:14235 (14.2 KB)
          Interrupt:19 Base address:0xd000 
 
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:65536  Metric:1
          RX packets:28 errors:0 dropped:0 overruns:0 frame:0
          TX packets:28 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:2124 (2.1 KB)  TX bytes:2124 (2.1 KB)

Another way is to use the ipfdown command to bring down the network interface.

[email protected]:~$ sudo ifdown eth0
Internet Systems Consortium DHCP Client 4.2.4
Copyright 2004-2012 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
 
Listening on LPF/eth0/08:00:27:85:68:81
Sending on   LPF/eth0/08:00:27:85:68:81
Sending on   Socket/fallback
DHCPRELEASE on eth0 to 192.168.1.1 port 67 (xid=0x69c9cbce)
avahi-daemon start/running, process 3209

And then it will not be active.

[email protected]:~$ ifconfig 
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:65536  Metric:1
          RX packets:108 errors:0 dropped:0 overruns:0 frame:0
          TX packets:108 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:8404 (8.4 KB)  TX bytes:8404 (8.4 KB)

Then bring it back up with the ifup command and it will be assigned an IP address.

[email protected]:~$ ifconfig 
eth0      Link encap:Ethernet  HWaddr 08:00:27:85:68:81  
          inet addr:192.168.1.7  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fe85:6881/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:111 errors:0 dropped:0 overruns:0 frame:0
          TX packets:178 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:15329 (15.3 KB)  TX bytes:21615 (21.6 KB)
          Interrupt:19 Base address:0xd000 
 
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:65536  Metric:1
          RX packets:124 errors:0 dropped:0 overruns:0 frame:0
          TX packets:124 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:9660 (9.6 KB)  TX bytes:9660 (9.6 KB)

This is not too difficult at all.

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