Error: A binding for this client already exists.

When attempting to add a reservation into a Cisco 1841 I encountered the following error message:

A binding for this client already exists.

when running:

client-identifier 0100.0111.001e.48

To resolve firstly identify which IP address the MAC address is assosiated with - this can be performed with:

show ip dhcp binding

Identify the assosiated IP and then simply run the following command to remove the binding:

clear ip dhcp binding <ip-address>

You should now be able to run the client-identifier command again.