Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

If you later enter the no shutdown command and the lease timer for the dynamic IP address has expired, the IP address is released.

When you enter the release dhcp command, although the IP address that was dynamically-acquired from a DHCP server is released from an interface, the ability to acquire a new DHCP server-assigned address remains in the running configuration for the interface. To acquire a new IP address, enter either the renew dhcp command at the EXEC privilege level or the ip address dhcp command at the interface configuration level.

If you enter renew dhcp command on an interface already configured with a dynamic IP address, the lease time of the dynamically acquired IP address is renewed.