I don't know if this will help, I don't quite understand the last steps myself, but this came from Cisco website. Will continue to research as I'm also using a 1200 but not as a DHCP.
_________________________________
Configuring Option 43 for 1100, 1130, 1200, 1240, and 1300 Series Lightweight Access Points
To configure DHCP Option 43 for Cisco Aironet 1100, 1130, 1200, 1240, and 1300 series lightweight access points in the embedded Cisco IOS DHCP server, follow these steps:
--------------------------------------------------------------------------------
Step 1 Enter configuration mode at the Cisco IOS CLI.
Step 2 Create the DHCP pool, including the necessary parameters such as default router and name server. A DHCP scope example is as follows:
ip dhcp pool
network
default-router
dns-server
Where:
is the name of the DHCP pool, such as AP1240
is the network IP address where the controller resides, such as 10.0.15.1
is the subnet mask, such as 255.255.255.0
is the IP address of the default router, such as 10.0.0.1
is the IP address of the DNS server, such as 10.0.10.2
Step 3 Add the option 60 line using the following syntax:
option 60 ascii "VCI string"
For the VCI string, use the value from Table G-1. The quotation marks must be included.
Step 4 Add the option 43 line using the following syntax:
option 43 hex
The hex string is assembled by concatenating the TLV values shown below:
Type + Length + Value
Type is always f1(hex). Length is the number of controller management IP addresses times 4 in hex. Value is the IP address of the controller listed sequentially in hex.
For example, suppose that there are two controllers with management interface IP addresses, 10.126.126.2 and 10.127.127.2. The type is f1(hex). The length is 2 * 4 = 8 = 08 (hex). The IP addresses translate to 0a7e7e02 and 0a7f7f02. Assembling the string then yields f1080a7e7e020a7f7f02. The resulting Cisco IOS command added to the DHCP scope is listed below:
option 43 hex f1080a7e7e020a7f7f02
