Wireless Access

For the AP to get an IP , this can be done from Controller ( if DHCP server is enabale on it ) or using external DHCP server

if i used external DHCP server , do i need to do any additional configuration on the DHCP server rather then what i do for normal  wired Pcs to get an IP from this DCHP Server (  do i need to do what is called DHCP Option 43 on DHCP Server sothat AP can get an IP , why ? )

You don't HAVE to have option 43, but it might be helpful.  If the APs and the controller are on the same subnet, you don't need it.  The APs will find the controller.  If the APs are on a different subnet than any of the controller interfaces, you need a way to discover the controller.  This can be via option 43 in the DHCP response (it should point to the controller-ip of the master controller) or DNS (by default the APs will try to resolve "aruba-master").  If you choose to use DNS, make sure the DNS suffix matches the record for aruba-master.

Thank  all  , it seems that DHCP Option 43 allows my DHCP server to provide the requesting AP with IP address of controller through the DHCP response ( ie : DHCP response will carry IP & Controller IP ) , right ?

Correct.  You may also need option 60.   Check the ArubaOS guide that Cjoseph mentioned below.  It walks through all the needed steps.

Thanks ,

i got it now

i already have read this appendix & got confused about some parts , but i feel now better . but for Option 60 can you just give a  hint about its usage 

My understanding is that option 60 is used to deteremine whether or not to send option 43.  If option 60 is "aruba-ap", then option 43 is sent back.

Someone please correct me if I am mistaken.

If the access point is in the same VLAN as the controller, it will find the controller via layer-2 broadcast.  if it is in a different subnet, you need to configure a DNS a-record of "aruba-master" and point it to the address of the controller, or (less desirable) DHCP option 43 and 60 on the DHCP server.  In the ArubaOS 5.0 Appendix A, there is a section "DHCP with Vendor-Specific Options" that tells you how to do this.  It is also in the ArubaOS user guide in the Appendix.

Yes, thats correct.  The Option 60 says "arube-ap" and option 43 is the controllers IP address in hex usually.  I typically use DNS as it's easier to put one record in the DNS vs. setting options on every single scope in the dhcp server. Also dhcp can be somewhat flakey depending on the dhcp server itself.