Post on 19-Jun-2015
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Basic Cisco WLAN Installation
Discovering and Associating with a Controller
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LWAPP ModesLightweight Access Point Protocol
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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
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Controller > General
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Access Point Association Sequence
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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
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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
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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
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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
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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
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Access Point Join PhaseWithout Master
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Access Point Join Phase Without Master (Cont.)
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Access Point Join Phase Without Master (Cont.)
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Access Point Join PhaseWithout Master (Cont.)
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Access Point Join Phase Without Master (Cont.)
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Access Point Join PhaseWith Master
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Access Point Join Phase With Master (Cont.)
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Access Point Join Phase With Master (Cont.)
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Access Point Join PhaseWith Master (Cont.)
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Access Point Join PhaseWith Master (Cont.)
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Primary Controller Name
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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.
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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
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AP States
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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
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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
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Controller Redundancy
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Controller Redundancy Designs—N + 1
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Controller Redundancy Designs—N + N
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Controller Redundancy Designs—N + N + 1
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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.
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