Linux dhcp client restart

How do I renew my DHCP lease?

Short of rebooting, how can I release and renew my DHCP lease? It would be useful to know a GUI and terminal method. I’d especially like to know if there is a means to do this without requiring admin privileges.

10 Answers 10

To renew your dhcp lease at the terminal:

sudo dhclient -r; sudo dhclient 

I think sudo service networking restart is a better way to go. What you suggest didn’t work for me on an 11.10 box with dhclient3. Instead, I ended up with two DHCP clients running: one dhclient3 and one dhclient . See ubuntuforums.org/showthread.php?t=1868368

sudo service network-manager restart in Ubuntu 13.10 64-bit desktop appears to properly restart network stuff and renew my DCHP lease. (From askubuntu.com/a/230751/2273 )

Useful to know for debugging: on Ubuntu 14.04 sudo service network-manager restart didn’t completely renew IP lease from DHCP. It just send a DHCP Request packet instead of a Discover . If you just want to renew your lease it’s enough, but if you are debugging DHCP you want to use the original solution.

Restarting networking isn’t a good way to go. I’m trying to do this on a remote machine. I will lose my access if I cut its networking. If it doesn’t come back, I’m screwed. No, blowing off all your network routes and taking the interface down is not a good solution to the problem «I want to renew a DHCP lease», just like getting out the shot gun is not a good solution to getting rid of a cockroach.

In my case I had to specify which card to renew:

Note: you might want to join the two on one line, as otherwise you might lose the remote connection you’re on after the first!

First release the current IP address:

then renew the IP address

.. or do them together to avoid losing connection:

sudo dhclient -r eth0 && sudo dhclient eth0 

Better: Join the commands with AND — sudo dhclient -r enp7s0 && sudo dhclient enp7s0 (replace with your eth network device)

Please edit this answer to join these together, I just got kicked off a remote box trying these separately.

for me, the change of IP was effective only after running netplan apply . Before, dhclient was showing a new IP, but it wasn’t used

In the network drop-down selector of the system tray you can press the network you are already connected to. This will make NetworkManager ask for a new lease from a DHCP server.

This also works for wired networks, but I don’t think it works for PPP connections (mobile broadband).

If you’re on a systemd based-version of Ubuntu without a GUI (i.e. server version) then this is the way to renew the DHCP lease:

sudo systemctl restart systemd-networkd 

Note: If you’re connected via the interface whose DHCP lease you’re renewing you may get disconnected, unless you’re connected via a statically configured interface or the console.

I was testing this with dhcpdump listening on other terminal. Didn’t seem to work, only the dhclient way.

If your machine is using dhclient then you would use that. In newer versions of Ubuntu dhclient is not used and instead the DHCP client in system-networkd is used.

This works on Ubuntu 12.04 LTS:

sudo service network-manager restart 

When I do that, Network Manager asks for a new DHCP lease.

I prefer this to manually (re)starting dhclient because I’ve had problems by stale dhclient processes (ones not managed by Network Manager) spontaneously and incorrectly reconfiguring my network settings at random points when it’s least convenient.

Still relevant on Ubuntu 16.04. dhclient -r just silently does nothing with a successful exit code otherwise. 🙁

Maverick comes with nmcli , a command line interface to the network manager.

I can’t see a simple way of telling it to renew a lease, but running:

Gets you a connection list, and running:

nmcli con down id 'Connection Name' nmcli con up id 'Connection Name' 

Takes the connection down and back up. It may be possible to do something similar with the device instead.

The connection list seems to include all connections, so this will probably work with PPTP and VPN connections too.

My DHCP server still shows the lease there. (I’m trying to force a release to make a static assignment take effect)

Having just upgraded to Maverick Meerkat Beta 1, something broke in my standard, vanilla eth0 configuration which I’ve not debugged yet. The quick and dirty workaround has been

which notices that there was a (possibly dead) client already and obtains a new lease:

There is already a pid file /var/run/dhclient.pid with pid 2436 killed old client process, removed PID file Internet Systems Consortium DHCP Client V3.1.3 Listening on LPF/eth0/00:1a:92:24:9c:85 Sending on LPF/eth0/00:1a:92:24:9c:85 Sending on Socket/fallback DHCPDISCOVER on vboxnet0 to 255.255.255.255 port 67 interval 3 DHCPREQUEST of 192.168.2.2 on eth0 to 255.255.255.255 port 67 DHCPACK of 192.168.2.2 from 192.168.2.1 bound to 192.168.2.2 -- renewal in 118389830 seconds. 

This isn’t a fix, just a hack. I’ll follow-up when I figure what went bad.

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Force DHCP Client to Renew IP Address – How to do

Wondering how to force DHCP Client to renew IP address? We can help you.

Some cable ISPs require their clients to notify the server if they wish to release an assigned IP address.

The dhclient command provides a means for configuring one or more network interfaces using the Dynamic Host Configuration Protocol, BOOTP protocol, or if these protocols fail, by statically assigning an address.

Here at Bobcares, we handle DHCP Client on servers of our customers as a part of our Server Management Services.

Today let’s see to force DHCP clients to renew IP addresses along with the steps that our Support Techs follow to do this.

Linux force DHCP client to release IP address and renew the IP address

The following are two methods to force DHCP client to release IP address:

Using the below command to force Linux to renew IP address using a DHCP for eth0 interface

For Ubuntu/Debian servers we can use the following command to restart the networking service and obtain an IP address via DHCP:

systemctl restart network.service

For CentOS/RHEL/Fedora we can use the following command to restart the networking service and obtain an IP address via DHCP:

systemctl restart networking.service

Use the following NetworkManager command to obtain info about Linux IP address and interfaces

To take down Linux interface enp6s0 and release IP address in Linux we can use the following command:

For obtaining a new IP address for Linux interface enp6s0 and release IP address using DHCP we can use the following command:

Some other basic commands to release IP address or renew the IP address

1. In Windows, we can release IP address using the command:

2. In Windows, we can renew IP address using the command:

3. To Linux renew IP command using DHCP

4. To obtain a fresh IP address using DHCP on Linux:

How to renew or release an IP in Linux for eth0

To renew or release an IP address for the eth0 interface, enter:

$ sudo dhclient -r eth0 $ sudo dhclient eth0

Other options in Linux to renew DHCP

We can also execute the following commands:

# ifdown eth0 # ifup eth0 ### RHEL/CentOS/Fedora specific command ### # /etc/init.d/network restart

### Debian / Ubuntu Linux specific command ### # /etc/init.d/networking restart

nmcli command (NetworkManager) to renew IP address in Linux

The nmcli is a command-line tool for controlling NetworkManager and getting its status. To renew IP address using nmcli for connection named ‘bobcares_5G’:

nmcli con // to get list of all connections nmcli con down id 'bobcares_5G' nmcli con up id 'bobcares_5G'

Linux Force dhclient to renew the IP address on a CentOS 7/Ubuntu/Debian and other Linux-based servers

Most modern Linux-based system uses the systemd as a init system and here is how to force Linux to renew IP address using DHCP. Use the IP command to find out the current IP address:

OR use the systemctl command to restart network service on a CentOS 7:

systemctl restart network.service systemctl status network.service

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Conclusion

In short, we saw the steps that our Support Engineers follow to force DHCP client to renew IP address

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How to configure the Ubuntu DHCP client

Dynamic Host Configuration Protocol, abbreviated as DHCP, is a client-server protocol that enables a DHCP server to assign an IP address and other related configuration parameters such as default gateway and subnet mask to a DHCP client on a network.

The DHCP protocol is necessary because it prevents network or system administrators from manually configuring IP addresses for new machines added to the network or computer system that are moved from one subnet to another.

Through the ’lease’, the DHCP server allocates the IP addresses to the DHCP clients. The lease time depends on how long the client system requires the connection or DHCP configuration.

We will talk about the configuration of a DHCP client on Ubuntu Linux distribution in this article. We have assumed in this article that the DHCP server is already set up on your other machine, or you can also install it from this URL.

DHCP client configuration on Ubuntu

To set up the DHCP client on your Ubuntu system, first, check the network interface name by running the following command:

Once the network interface name is identified, you need to make some changes to the network interfaces file for DHCP client configuration. So, open the ‘/etc/network/interfaces’ file in your favorite text editor by using the following command:

Now, use the following syntax to configure the dhcp client:

Here, the network interface name is ‘enp1s0’; we have changed the above lines into the following format:

Save and close the above configuration file. Now, restart the network manager services by running the following command:

Verify the NetworkManager service running status by executing the following command:

When during the booting process, this system should request network parameters from the DHCP server.

To manually execute the DHCP process, the dhclient command can be used. If the DHCP server assigns no IP to the DHCP client, then use the following command renew or release the IP address. Wait for a while; the DHCP server will automatically assign IP addresses to the client machine.

Using the ‘ifconfig’ command can view the interface name.

Configure DHCP through netplan

In most Ubuntu distribution, networking is controlled or managed through the netplan program. Therefore, in this situation, you need to edit the netplan configuration files. To edit the appropriate file configuration, navigate into the ‘/etc/netplan’ directory and open that file.

Add the following lines in this file:

Save the above configuration by using ‘Ctrl+O’ in this file and exit from this window by pressing ‘Ctrl+x’.

Now, run the below-mentioned command to apply changes:

Configure DHCP client through Ubuntu desktop environment

You can also use another virtual machine with Ubuntu 20.04 Desktop as a DHCP client. In Ubuntu, the default configuration method is set as DHCP. If it does not take an IP director from the DHCP server, change the IPV4 setting of your network. Click go into the ‘Setting’ and move into the network wired or wireless settings. The following window should display on your system:

Set your entire IPV4 configuration similar to the above-displayed screenshot.

Now, show the network details by clicking on the ‘Detail’ tab as follows:

Verify the configuration by running the following command:

You will see that the IP is allocated to the network interface.

You can also use the host machine on your system as a DHCP client. However, to get IP, do not reboot your host machine because, in this case, Virtualbox will be powered down, so there is no DHCP running on the system.

It is important to note that if you are using mobile devices or host machines as a DHCP client, most of the chances are that they have already been connected to this network. However, they will request the same IP to the DHCP server that was allocated before. However, if the IP does not fall in your defined range then, a request will be sent to the router.

Conclusion

We have seen in this article how to configure a DHCP client using different ways on Ubuntu distribution. All commands we have implemented on the Ubuntu 20.04 environment. DHCP client configuration is very simple. So that, in just a few minutes, you can easily set up a DHCP client on your system using the above-mentioned steps.

About the author

Samreena Aslam

Samreena Aslam holds a master’s degree in Software Engineering. Currently, she’s working as a Freelancer & Technical writer. She’s a Linux enthusiast and has written various articles on Computer programming, different Linux flavors including Ubuntu, Debian, CentOS, and Mint.

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