Force DHCP Client to Renew IP Address - Perform it now








Are you trying to force DHCP Client to renew IP address?

This guide is for you. 


A DHCP client automatically attempts to renew its lease as soon as 50 percent of the lease duration has expired. The DHCP client will also attempt to renew its IP address lease each time that the computer restarts.

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 Ibmi Media, as part of our Server Management Services, we regularly help our Customers to handle DHCP Client on servers.

In this context, we shall look into how to force DHCP clients to renew IP addresses.


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:


Method 1

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

$ dhclient -v -r eth0

Method 2

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

Method 3

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

$ nmcli con

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

$ nmcli con down id 'enp6s0'

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

$ nmcli con up id 'enp6s0'


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

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

$ ipconfig /release

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

$ ipconfig /renew

3. To Linux renew IP command using DHCP

$ sudo dhclient -r

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

$ sudo dhclient


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

OR

### 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 'ibmimedia_5G':

$ nmcli con // to get list of all connections
$ nmcli con down id 'ibmimedia_5G'
$ nmcli con up id 'ibmimedia_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:

$ ip a
$ ip a s eth0

Run:

$ dhclient -v -r eth0

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

This article covers how to force DHCP client to renew IP address. You need to use Dynamic Host Configuration Protocol Client i.e., dhclient command. 

The client normally doesn't release the current lease as it is not required by the DHCP protocol. 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.


Linux renew ip command using dhcp:

The -r flag explicitly releases the current lease, and once the lease has been released, the client exits. 

For example, open terminal application and type the command:

$ sudo dhclient -r

Now obtain fresh IP address using DHCP on Linux:

$ sudo dhclient


To start DHCP client in Linux:

1. To start the DHCP service, type the following command: # /etc/init.d/dhcp start.

2. To stop the DHCP service, type the following command: # /etc/init.d/dhcp stop. 

The DHCP daemon stops until it is manually started again, or the system reboots.


How can I 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

In this example, I am renewing an IP address for my wireless interface:

sudo dhclient -v -r eth0

sudo dhclient -v eth0


Command to release/renew a DHCP IP address in Linux:

1. ip a - Get ip address and interface information on Linux

2. ip a s eth0 - Find the current ip address for the eth0 interface in Linux

3. dhclient -v -r eth0 - Force Linux to renew IP address using a DHCP for eth0 interface

4. systemctl restart network.service - Restart networking service and obtain a new IP address via DHCP on Ubuntu/Debian Linux

5. systemctl restart networking.service - Restart networking service and obtain a new IP address via DHCP on a CentOS/RHEL/Fedora Linux

6. nmcli con - Use NetworkManager to obtain info about Linux IP address and interfaces

7. nmcli con down id 'enp6s0' - Take down Linux interface enp6s0 and release IP address in Linux

8. nmcli con up id 'enp6s0' - Obtian a new IP address for Linux interface enp6s0 and release IP address using DHCP


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