We have a setup of two WiSMs (4 WLCs) in the HO and multiple branches connected to the
HO through MPLS with the same ISP.
In one of the branches, the APs are unable to join any of the cotrollers. I
troubleshooted this issue from different aspects with no success.
The APs are getting the management IP address of the four WLCs through DHCP option 43:
ip dhcp pool AccessPoints
network 10.3.3.0 255.255.255.0
option 60 hex 4369.7363.6f20.4150.2063.3132.3430
option 43 hex f110.0a63.0601.0a63.0602.0a63.0603.0a63.0604
Which translates into 10.99.6.1, 10.99.6.2, 10.99.6.3, 10.99.6.4
I captured the APs traffic and found out the following:
- the APs get the controller IPs and send LWAPP discovery requests to all of them.
- LWAPP Discovery responses arrive at the APs from all of the four WLCs.
- APs send LWAPP join requests to all the AP Manager IPs of the WLCs.
According to Cisco documentation, the AP will pad the packet with additional data
until it exceeds the 1500 Byte MTU size and then sends it again with less padding
until it doesn't get fragmented.
The problem happens when the first LWAPP join request is sent from the APs. It gets
fragmented and never reaches the WLCs. Consequently, the APs give up immediately and
never send a subsequent LWAPP Join request and keep reloading and repeating the same
Even after I configured one AP as H-REAP and with static WLC IP addresses, it still faces the same issue.
I captured the fragmented packets that reached the HO from this H-REAP. Please find them attached to
I need to know what to do in order to allow the join request to reach the controllers.
There is no Firewall blocking the traffic, any traffic to the entire HO subnetwork is