Explanation/Reference:
Section:
Considerations for Expanding an Existing Network Explanation
Explanation:
When you add a lightweight access point (LAP) to a Wireless network that uses Lightweight Access Point Protocol (LWAPP), the LAP goes through a sequence of steps to register with a Wireless LAN controller (WLC) on the network. First, if Open Systems Interconnection (OSI) Layer 2 LWAPP mode is supported, the LAP attempts to locate a WLC by broadcasting a Layer 2 LWAPP discovery request message. If a WLC does not respond to the Layer 2 broadcast, the LAP will broadcast a Layer 3 LWAPP discovery request message.
Once a WLC receives the LWAPP discovery message, the WLC will send an LWAPP discovery response message to the LAP; the discovery response will contain the IP address of the WLC. The LAP compiles a list of all discovery responses it receives. The list is cross-referenced against the LAP's internal configuration. The LAP will then send an LWAPP join request message to one of the WLCs on its list of responses.
If the LAP has been configured with a primary, secondary, and tertiary WLC, the LAP will first send an LWAPP join request message to the primary WLC. If no response is received from the primary WLC, the LAP will try the secondary and tertiary WLCs in sequence. If no response is received from either the secondary or tertiary WLCs, the LAP will examine the responses on its list for a master controller flag. If one of the WLCs is configured as a master, the LAP will send an LWAPP join request message to the master WLC. If there is no master configured, or if the master does not respond, the LAP will examine its list of responses and send an LWAPP join request message to the WLC with the greatest capacity.
When a WLC responds with an LWAPP join response message, the authentication process begins. After the LAP and the WLC authenticate with each other, the LAP will register with the WLC.
Reference:
Cisco: Lightweight AP (LAP) Registration to a Wireless LAN Controller (WLC): Register the LAP with the WLC