I run a router at home with dd-wrt. My main machine has a static IP lease based on the MAC address. Sometimes when I reboot the main machine the static IP is not properly released by the DHCP subsystem and the router holds on to it, therefore assigning my machine a regular DHCP IP.

To fix this without having to reboot the machine, follow these steps:

1. Login to the dd-wrt router.
2. Go to the Setup page and click the Save button followed by the Apply button. This will restart the DHCP daemon in the router without having to reboot it.
3. Go to the Status page on the router and click on the Lan tab and verify that the IP was indeed released.
4. On the main machine, run the following commands:

   1 2	sudo dhclient -v -r enp4s0 sudo dhclient -v enp4s0

The above will renew the IP lease to the default static IP assigned to that MAC address. Note that the above assumes you are using NetworkManager with dhclient under it and that your network interface is enp4s0.