Check this link -

http://forum.tp-link.com/showthread.php?81286-EAP110-wont-assign-IP-addresses-to-wireless-devies-while-connecting

The EAP120 has no DHCP server functionality.

Steve

@ Steve
that's why I post it here to get some help and thanks for your post but it wont solved my and the other users who need to configure the dhcp server on the AP.
this is for Business solutions and TPLINK just ignored the problems???
its kind of what the heck ..when I noticed it has no dhcp server settings.
even the cheapest tplink AP have dhcp server functionality.

@Matchie

I agree in part with you, as there's several things I have brought to TP-Links attention where the EAP120s and EAP controller software can be improved.

Perhaps we should start a feature request post?

As for your immediate problem, I'm sorry I can't be more helpful specifically with configuring the EAP120.

Without knowing more about your infrastructure its difficult to recommend a solution, but have you considered a cheap router to act a DHCP server, perhaps running with a VLAN to segregate the WiFi traffic?

Steve

For certain forms of servers, you need to assign a static scientific discipline address and subnet mask throughout or when Setup. These servers embrace DHCP servers, DNS servers, WINS servers, and any server providing access to users on the net. See here to more info, it's additionally suggested that you simply assign a static scientific discipline address and subnet mask for every domain controller. If a pc has over one network adapter, you need to assign a separate scientific discipline address for every adapter.

In my world, an AP does nothing else but being an Access Point. No DHCP server, or anything like that. Thats a router/server functionality.

DHCP normally appears on combined router/accesspoint for SOHO use.