1. Lightweight Access Point Protocol (LWAPP) can operate at either Layer 2 using Ethernet or Layer 3 using IP for communication between wireless access points (APs) and wireless controllers. 2. During discovery, an AP will try to find available controllers using Layer 2 or Layer 3 methods like broadcasts or DHCP options. It will then select the best controller to join based on its configuration or network conditions. 3. Once associated, the controller uses LWAPP messages to securely configure the AP and monitor its state. Good designs plan for redundancy of both APs and controllers to ensure wireless connectivity.

1. Basic Cisco WLAN Installation Discovering and Associating with a Controller

2. LWAPP Modes Lightweight Access Point Protocol

3. Layer 3 Lightweight AP Protocol (LWAPP) Layer 3 LWAPP is in a UDP/IP frame Cisco WLAN controller and AP can be connected to the same VLAN/subnetwork or connected to a different VLAN/subnetwork Requires Cisco AP to obtain an IP address using DHCP Control traffic is encrypted, data is not

4. Controller > General

5. Access Point Association Sequence

6. AP LWAPP Discover and Join Overview AP issues a DHCP DISCOVER to obtain address AP attempts Layer 2 controller discovery AP attempts Layer 3 controller discovery LWAPP discovery broadcast on local subnet Over-the-Air provisioning (OTAP) Local stored controller IP address from prior successful join process DHCP option 43 DNS resolution of CISCO-LWAPP-CONTROLLER After AP discover controllers, it selects and joins one via primary, secondary, tertiary, or master configuration of controllers

7. AP LWAPP Discovery AP obtains an IP address Statically defined DHCP discover AP tries to connect to a controller using Layer 2 then Layer 3 LWAPP (LWAPP only models), or Layer 3 LWAPP (Cisco IOS-based models) Layer 3 LWAPP discovery order: Subnetwork broadcast mode Connect Cisco AP directly to, or same subnet as, a Cisco controller to learn Cisco controller IP address Cisco AP will send a subnetwork broadcast

8. AP LWAPP Discovery (Cont.) Over-the-air provisioning (OTAP) Connect Cisco AP in range of another already connected AP Configure the controller to allow OTAP Cisco AP will receive information about controllers from its neighboring APs AP priming Connect Cisco AP directly, or same subnet as a Cisco controller to learn Cisco controller mobility group IP addresses Move Cisco AP to a remote network and have it use DHCP for a local and gateway address Cisco AP will send a subnetwork broadcast discovery request to the primary controller and all controllers in the learned mobility group

9. LWAPP Layer 3 Discovery DHCP vendor option mode Place Cisco AP on remote network and have it use DHCP for a local and gateway address Use DHCP extension to learn a Cisco controller management interface IP address from extension Option 43 DNS/DHCP vendor option mode Place Cisco AP on remote network and have it use DHCP for a local and gateway address Use DHCP extension to learn a DNS IP address Cisco AP will then make an address resolution call using the hostname CISCO-LWAPP-CONTROLLER, which should be configured to return the management interface IP address of available controllers

10. Access Point Join Order Response from primary, then secondary, and finally tertiary configured controller If no configured controller, response from a master controller If no master controller response, response from the least loaded controller Least loaded AP-Manager interface or least loaded controller

11. Access Point Join Phase Without Master

12. Access Point Join Phase Without Master (Cont.)

13. Access Point Join Phase Without Master (Cont.)

14. Access Point Join Phase Without Master (Cont.)

15. Access Point Join Phase Without Master (Cont.)

16. Access Point Join Phase With Master

17. Access Point Join Phase With Master (Cont.)

18. Access Point Join Phase With Master (Cont.)

19. Access Point Join Phase With Master (Cont.)

20. Access Point Join Phase With Master (Cont.)

21. Primary Controller Name

22. Controller > Advanced > Master Controller Mode Master controller configuration should only be used for provisioning APs to associate them to a particular controller and then to assign a primary controller.

23. AP LWAPP Join Messages LWAPP join request Includes type of controller and MAC address of controller Includes AP hardware and software version Includes the name of the AP issuing the join request Indicates the number and type of radios present in AP Includes a certificate payload for establishing a secure connection Includes a session payload to setup the session value Includes a test payload to test the ability of the network to support jumbo frames LWAPP join reply Includes a result code Includes controller’s certificate payload response Includes a test payload to test the network’s ability to support jumbo frames

24. AP States

25. LWAPP Configuration Phase The LWAPP configure request: Wants the controller to provide configuration data Provides the controller with a list of configurable parameters and the current values The LWAPP configure response: Provides configuration values for the AP Allows the controller to override requested configuration elements from the AP. Includes configure command packets. Causes the AP: To evaluate each configuration element To begin implementing the configuration elements

26. Design: AP Redundancy AP redundancy RF “self-healing” allows system to compensate dynamically for lost APs System must be designed to support self-healing Distance between APs determines redundancy limits

27. Controller Redundancy

28. Controller Redundancy Designs — N + 1

29. Controller Redundancy Designs — N + N

30. Controller Redundancy Designs — N + N + 1

31. Summary LWAPP can operate at Layer 2, using Ethernet or Layer 3, using IP. An LWAPP AP will try to discover as many controllers as possible, using Layer 2 or Layer 3 methods. It will then choose to join the best controller, based on configuration or network elements. Once associated to a controller, it will receive its configuration using a secure connection. A good design should plan for AP redundancy but also controller redundancy.