In order to have an easy overview of dhcp connected clients, I have set the "client id" field in the DHCP tab of the Network Preferences (for wired and wireless interfaces). I have done that on all my idevices (iMacs, iPhones, iPad). The result is quite annoying : for one of my iMacs (all iMacs are under Lion except one under SL) the DHCP client id reported by Airport utility (v5.6) is exactely what I have manually set (and I can have a different id for the wired and wireless I/F). For all others iMacs the client id I have set is replaced by the computer name as defined in the Sharing prefs (with spaces replaced by dashes); for those computers, the displayed client ids are the same for both wired and wireless interface whatever I put in the Client Id field.
My only clue is that the only iMac for which things are working as expected is the newer oner that have been bought with SL and upgraded to Lion. Others Macs where first Tiger Macs that have been upgraded to Leopard then SL and finally Lion for most of them).
But that's not all. When I started "debugging" this behaviour, I noticed that none of my portable devices where identified by their client id. After reading some posts in this forum, I discovered the required settings for iPhone & iPad : It worked : the client id displayed in the Airport utility was exactely the one I specified. But few hours later, the client id name of most my iPhone/iPad was changed into the device name (given in iTunes) (again with spaces replaced by dashes).
Quite difficult to give a general rule (in addition, Airport Utility v6 which only shows wireless client id have a different behaviour...).
Why do I want to use DHCP through client ID ? Because using using DHCP through MACaddress while using Bootcamp gives the same IP address to Bootcamp and Lion which is an unwanted behaviour for me.
If someone has clue, your welcome ;-)