DHCP and domain name

["Johan Mazel" <johan.mazel@gmail.com>]

Hi
I have a Debian 2.6.18-4-686 running with KDE 3.5.5. 

I have three questions.

1) When I start the system, my IP address is 
192.168.0.72. If I make a renew of ip address with dhclient, my IP address change 
192.168.0.20. If I change again, my IP address stay at 
192.168.0.20.
Is that possible that at the startup of the computer, the network component just assign a choosen IP without asking the DNS ?

2) I captured the frames with Wireshark (during the renewal of
IP address) and the DHCP server send me a new address with a domain
name.
Is there anyway to access this domain name ?

3) The command hostname --fqdn returns me : 
localhost.localdomain.
Is that linked with the fact that I'm on a local network ? It seem that yes, but I'm sure.
How can I change the fqdn ?

Thanks.

Johan