Lightweight Access Point Registration with Wireless LAN Controller (WLC)

hello everyone welcome to cisco support community I am rajesh from the cisco support group as promised in my last video today we will learn about one of the most important processes that happens in a Cisco Unified wireless lab we'll understand how the integral components of the Cisco wireless solution the lightweight access point and the wireless LAN controllers talk to each other and establish communication before they start servicing wireless clients this is called the lightweight access point registration process access points are broadly classified into two types we have the standalone ApS also known as the autonomous a piece or the distributed APs and we have the centralized ApS thin ApS more commonly known as the lightweight access points in a Cisco Unified wireless network we use lightweight access points the lightweight access points are zero touch deployed and no individual configuration of access point is required they have to first discover controllers and register with them before they can start servicing wireless clients let us now look at the wireless LAN controller discovery process the lightweight access point registration process is a four-step process first the AP needs to get an IP address next the access point needs to find candidate controllers to which it can register the third step is to select a controller from the list of candidate controllers and the final step is to register with the wireless LAN controller let us now see how the lightweight access point accomplishes these steps and completes the registration process once the lightweight access point boots up the first thing it does is look for an IP address assuming we have an out-of-the-box lightweight access point it sends a DHCP discover message hoping to hear from DHCP servers in the network DHCP servers which receive the DHCP discover respond and provide an IP address optionally the DHCP server can also be configured to return other information as we'll see shortly all right a lightweight access point has received an IP address from the DHCP server next it needs to find controllers to which it can register for this the access point uses the wireless LAN controller hunting algorithm let us now see how the wireless LAN controller hunting algorithm works the hunting algorithm supports two types of controller discovery Leigha to discovery and layer three discovery layer to discovery is supported only on few of the older platforms of controllers and access points using L map capo app does not support layer 2 discovery layer 3 discovery is supported on all platforms either with l web or cap gap though via the hunting algorithm work phase if lead to discovery is supported the access point since a discovery request in an Ethernet broadcast if the ap does not find any controller using this method or if mayor to discovery is not supported the AP proceeds to layer 3 discovery and if the AP does not find controllers using layer 3 discovery it reboots and starts all over again let us now look at layer 3 discovery methods in detail as discuss the lightweight access points use the layer 3 discovery algorithm if lay to discovery method is not supported or if relate to discovery method fails the layer 3 discovery algorithm uses different options in order to discover controllers and to build a controller list let us now look at the various options by which layer 3 discovery is done first the access point broadcast a layer 3 discovery message on its local IP subnet any wireless LAN controller configured for layer 3 mode that is connected to the local IP subnet will receive the layer 3 discovery message and reply with the unicast discovery response to the access point next when a feature called over-the-air provisioning is enabled on a controller access points that are already joined to the controller advertise their known controller IP addresses in neighbor messages that are sent over the air new access points attempting to discover controllers receive these messages and then unicast a discovery request to each controller controllers receiving the discovery requests unicast our discovery response to the access point access points also maintained previously learned control IP addresses locally in its NVRAM they use these IP addresses and sent a unicast discovery request to each of the controller addresses any controller which if the discovery is request/response by sending a discovery response to the access point the next one is an interesting one DHCP servers can be programmed to return controller IP addresses in vendor-specific option option for the three in the DHCP offer of the lightweight access points when an access point gets an IP address where DHCP it looks for controller IP addresses in option for the three feet in the DHCP offer the access point will send the unicast discovery request to each controller IP address listed an option for the three again the control is receiving the discovery request unicast a discovery response to the access point and last the access point will attempt to resolve the dns name Cisco - L vApp - controller dot local domain when the access point is able to resolve this name to one or more IP addresses the access point sends a unicast this curve is a quest message to the resolved IP addresses each controller is seeing the discovery request replies with the discovery response to the access points the lay three discover the algorithm repeats until at least one controller is found during the lay three wireless LAN controller discovery the access point always completes all the steps that we have discussed in order to build a list of candidate controllers after the access point has completed the discovery step the access point selects a controller from the candidate list using a selection algorithm which we will be seeing in the next slide the discovery response message sent by a controller in reply to a lightweight access point contains certain important parameters which is used in the controller selection process some of these parameters include the controller system which is the host name of the controller the controller type which defines the platform of the controller the controller's AP capacity and its current load the master controller flag and the a/b manager IP address let's now see how the selection algorithm uses some of these parameters for controller selection all right we are all set to select the best controller from the list of candidate controllers using the wireless LAN controller selection algorithm the lightweight access points use three criterias to select the best controller if the access point has been previously configured with the primary secondary or a tertiary controller the access point will attempt to join these first if not it will attempt to join the controller configured as a master controller if both these criterias fail the access point will join a controller with the greatest excess capacity now that we have selected a controller using the selection algorithm we move on to the join process after the access point selects a controller the access point sends a joint request in the wireless LAN controller in the join request the access point Mbits a digitally signed x-dot 5:39 certificate when the certificate is validated the controller sends a joint response in order to indicate to the lab that it is successfully joined to the controller controller also embeds its own digitally signed X dot fiberline certificate in the join response that the access point must validate after the access point validates the certificate the join process is complete we are now in the final step of completing the registration process of the access point with the wireless LAN controller in the post join process the access point downloads firmware from the controller if it's running a code version which does not match with the controller after sinking of the firmware versions between the controller in the access point the controller provisions the access point with appropriate a society security QoS and other parameters that have been configured on the controller once this is done the access point is ready to serve wireless LAN clients and this completes the registration process now the access point is registered with the wireless LAN controller I hope the information provided in this video was useful Lupo's recommencing feedbacks on what kind of videos you would like to see on the cisco support community thank you

Channel: Cisco Community

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Keywords: 2100 wlc, 4400 wlc, 5500 wlc, lap, controller, wlc, access-point, controllers, registration, wlc4402, expert_video

Id: oOh_Iv1CHxQ

Length: 8min 38sec (518 seconds)

Published: Thu Oct 13 2011