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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