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Cisco Access Points & Layer 3 Networks

We have had a wireless deployment on a layer 2 network for several years and it has worked very well.  Now we are deploying layer 3 switches in our data closets and found an issue with deploying new access points.  We now have to connect a new access point to a layer 2 switch prior to installing on a layer 3 switch.  If we connect the ap first to a layer 3 switch, it will never find a controller.  I don't know what I am missing.  Does anyone have any information regarding this issue?  TIA

Community Member

What Im thinking is the AP on

What Im thinking is the AP on L2 is finding the controller based on CAPWAP broadcast and then download the configuration form the WLC and after that it has the stored info available some how. 

I believe the AP on L3 has trouble finding the WLC. One good reason could be due misconfiguration on your routing between subnet . 

AP goes through this process:

CAPWAP discovery broadcast: is this working fine? do you have a proper routing in between VLANs? do you forward the CAPWAP protocol from AP vlan to WLC Vlan? 


Passing through the L3 switches for CAPWAP if the WLC is not the DHCP server (if it is we can use ip helper-address x.x.x.x)

Ip forward-protocol udp 5246 (New CAPWAP)

Ip forward-protocol udp 1222 (Old lWAPP)

one more thing is are you using LWAPP or CAPWAP capable AP. this is something else you need to check because LWAPP is layer 3 capable


Over-the-Air (you possibly wont use it)

Locally stored WLC IP address - this is what happen after the L2 boot I believe but not the case on L3

DHCP option 43: what happens when you add this to your dhcp? the AP should see this option and the hex info of the IP must be available to them. Unless the APs has trouble even finding the DHCP server which points you to the routing misconfiguration again. 


DNS Cisco-CAPWAP-Controller ?have you tried this too? 


My bet is still on some misconfiguration between your vlans and L3 routing. the APs tries to find the WLC but cant get there because of that. 


VIP Purple

There is nothing wrong with

There is nothing wrong with your L3 network (if it is even 2nd time AP won't register to your WLC). Unless your WLC & AP are on the same L2 network you have to configure a method (DNS, DHCP Option 43, Broadcast forwarding or static) as highligted by "babakkhorshid".in the above for APs to discover a WLC.

Once AP register to a WLC, it will remember those details in a permanent memory, that's why once you connected to  your L2 network it learn & register to WLC using same subnet broadcast ( & then when you connected L3 network AP used previously learnt WLC to send AP join messages. Since your L3 working fine, AP has the reachability to WLC & get register.

Here is some reference information about how AP register to a WLC. DHCP option 43  or DNS is common method used.




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