Existing wlc setup uses local dhcp on subnets but I can't see where this is set up?

[wpflum]

Let's start out with a bit of topology, we have a main location connected as a hub/spoke to three remote locations using fiber.  The main location is 10.1.2.0/25 and each remote is a separate sub net, 10.2.2.0/24, 10.3.2.0/24 and 10.4.2.0/24.  Each location has a Cisco router handling the internet connection that each location has separately along with the fiber connections between locations, so for locations equals four separate  internet connections physically connecting at each location.  Each location has its own dhcp server.  The company that set up the wifi set it up with a single AIR-CT2504-K9 server at the main location handling the remote Access Points but had it sending all dhcp requests to the main sub net 10.1.2.0/24 so anyone at the remote locations couldn't see local printers or network resources.  The eventually got it working so that each remote location uses the local dhcp so a phone connecting have the sub net of the remote location instead of the sub net of the main location.

That is the setup now.  I'm working on finishing up some things they never finished, we got tired of them taking forever to finish up things already agreed to and paid for, but before I do too much I want to make sure I understand how they did handled the dhcp stuff so I don't blow up that by accident.  The kicker is I really don't see anything in either the GUI or the cli that points the APs to use the local dhcp they are connected to.  They get an IP from the dhcp and when connecting to a device the device gets an IP from the local dhcp but nothing stands out that would make them do this.  Obviously this is working but I'm stumped.  I've also used the console connection to an AP to see it's programming and don't see anything standing out that could make it do what it does. 

Any ideas how this could have been done that I can look for?

[Rasika Nayanajith]

First check AP configured as "Local Mode" or "FlexConnect Mode". You can check this simply go to WLC GUI interface and select individual AP.

Next thing I would check is specific WLAN (SSID configuration). I assume that WLAN is configured with FlexConnect local switching (see under WLAN -> Advanced ). If that is the case, your SSID traffic terminates on the local switch and you map particular local vlan under FlexConnect Group (WLAN -> VLAN mapping)

DHCP configuration may be on local switch SVI where that SSID traffic map to

HTH

Rasika

*** Pls rate all useful responses ***

[Theodore April]

to add to Rasika has said - check SVI  there might be a Helper ID
 
interface ethernet0/0
 ip address 192.168.100.1 255.255.255.0
 ip helper-address 10.55.11.3
 
DHCP IP Helper addresses are IP addresses configured on a routed interface such as SVI or a routers Ethernet interface that allows that specific device to forwards DHCP request it receives on an interface to the DHCP server specified by the IP Helper address

[Rich R]

And to add my bit to the other 2 :) ...
Assuming the APs are in flexconnect local switching mode the DHCP is just sent out on the local LAN/VLAN exactly the same as any wired client would be so the response will come from whatever local DHCP server is configured on the local router or switch or even a dedicated DHCP server. You mentioned you have a router at each location so that's likely where the DHCP pool is configured.

Apart from the basic flexconnect local switching configuration no special DHCP config is needed on WLC or AP for this to work because the AP is just bridging the traffic (including the DHCP) to the local VLAN.