Cisco Support Community
Community Member

How does CAPWAP work when an LWAP and WLC are not on the same subnet?

Reading various Cisco documentation and Vinay Sharma’s document ("AP fails to join controller" - Lightweight Access Point (LAP) fails to join Wireless LAN controller (WLC, I understand:


“When the LAP powers up, it sends out a DHCP request, with the hope that a DHCP server will provide an IP address. After the LAP gets an IP address from the DHCP server, the LAP broadcasts a Layer 3 LWAPP discovery message on to its local subnet. Because the WLC is also on the same subnet, the WLC receives the LWAPP discovery request from the LAP and responds with a Layer 3 LWAPP discovery response.”



  1. What happens if the LAP and the WLC are not on the same subnet?  By default, a router/layer 3 device will STOP all broadcast. 
  2. How does CAPWAP/LWAPP get around this?  In our network, no LAP is on the same subnet as the WLC.  So I am not sure how they are working. 


Thank you


T.J. Reed

Everyone's tags (1)
VIP Purple

Hi Reed,L3 broadcast is one

Hi Reed,

L3 broadcast is one method of WLC discovery, There are other methods too (DHCP option 43, DNS, Broadcast forwarding, static config, etc). So you have to use any other method in your case.

Below blog post may help you understand this in bit detail



*** Pls rate all useful responses ****

VIP Purple

Hi,APs on a different subnet


APs on a different subnet then you have to

1. configure DHCP option 43 on the APs subnet

2. put in a DNS entry for CISCO-LWAPP-CONTROLLER.localdomain

3. Use IP helper address on the Router


Check step 4,5& 6 in Layer 3 LWAPP WLC Discovery Algorithm:


Hope this helps you to understand.



Dont forget to rate helpful posts

CreatePlease to create content