Speed up DHCP during boot

[Ingo Huber]

I am running ubuntu on a laptop, that contains a pci lan card and, from 
time to time, wireless pcmcia.

Both devices are recognized during boot, but dhcp connection tests waste 
a lot of time, if a device is not connected at all. If I am on wireless 
only, f.e., the boot dhcp procedure takes a bout 10 seconds to ask for 
ethernet dhcp, until it gives up. If I am on lan, and have'nt my 
wireless card plugged in, the same happens asking for the wlan's dhcp. 
Needless to say, there is never a need to have both connected. So 
booting takes it's time asking for dhcp.

I don't know that behaviour from archlinux or linux from scratch, 
therefore there should be a way to change it.

Any hint for me?