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LESSON 7 - WIRELESS

michael.0lsn WIRELESS 2 Englisch 42 Karten

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  1. 1Autonomous APs have their ownInter-Networking Operating System. (IOS)
    No centrallized point of management. Every AP configured seperately.
  2. 2This feature will allow for at least some centralization of services for autonomous APs.WDS
    Wireless Domain Services
  3. 3All transmitted data is sent via an encapsulation protocol calledLightweight Access Point Protocol (LWAPP)
  4. 4Client data is encapsulated with an LWAPP header that contains vital information about the clientsReceiver Signal Strength Indicator (RSSI)
    &
    Signal-to-Noise Ratio (SNR)
  5. 5LWAPP carries and encapsulates control information betweenAP and the WLC over an encrypted tunnel.
  6. 6A couple of great benefits gained through this kind of centralized control are improved securityimproved security and traffic conditioning.
  7. 7Any APs found not to be LWAPP capable are classified asrogues.
  8. 8For physical security reasons, the configuration of the AP resides only inRAM while in operation and connected to the WLC.
    This way, the configuration can't be snagged from the AP once that device has been removed from the network.
  9. 9The CUWN consists of five elements that work together to provide a unified enterprise solution:- Client devices
    - APs
    - Network Unification
    - Network Management
    - Mobility services
  10. 10Lightweight architecture allows for the splitting of802.11 Data Link layer functions between the lightweight AP and the WLC
  11. 11Split MACThe Lightweight architecture allows Splitting of the 802.11 Data Link Layer functions between the lightweight AP and the WLC.
    The LAP handles real-time portions of the communication.
    The WLC handles items that are not time-sensitive.
  12. 12Split MAC Real-Time portions handled by the lightweight AP:-Frame exchange handshake between client and AP
    -Beacon frame transmission
    -Handling of frames for clients in power save mode
    -Responses to probe request frames from clients and the relaying of received probe requests to the controller
    -Transmission to the controller of real-time signal quality
    -RF channel monitoring for noise, interference, other WLANs, and rogue APs.
    -Encryption and decryption (layer 2 wireless only), with the exception of VPN and IPSec clients.
  13. 13Split MAC Non-Time-Sensitive portions handled by the WLC:-802.11 authentication
    -802.11 association and re-association (mobility)
    -802.11 to 802.3 frame translation and bridging
    -The termination of all 802.11 frames at the controller
  14. 14LWAPP runs between the AP and the WLC and performs some important tasks. One of its jobs is to encapsulate and encrypt information called:Control data.
    Control Data is information about the wireless environment that's vital to the wireless infrastructure.
  15. 15Impressively, you can configure and control up to ________ WLANs for each AP on a single WLC.16
  16. 16The WCS tool is used to managemultiple WLCs.
    WCS - Wireless Control Systems
    *In the same way that a WLC can send a configuration to APs, the WCS can send configurations to multiple WLCs.
  17. 17WCS is management software that you install on a Linux of Windows server. You configure it through HTTPS, and it gives you the ability to manage hundreds ofWLCs.
    The WLCs dont even have to be on the same LAN - they can be physically located in offices in different countries if necessary!
  18. 18Lightweight APs associate with a specified WLC used to control the AP and can also prode the APs with firmware upgrades. An AP has to locate its particular WLC before it can associate with it, this process is called:Discovery and Association.
  19. 19The order of the discovery method:Subnet Broadcast
    AP Priming
    DHCP option 43
    Domain Name System (DNS)
    Flash
  20. 20After you complete the necessary discovery steps and send out a discovery message, it's possible an AP can sometimes get a bunch of responses from controllers. Because of this, there's a specific order an AP uses to select the WLC to register with.If there isn't any controller information primed in the AP, it will simply look for a master controller, which defined when you create a mobility domain. But if the AP has been primed, it will try to associate with its PRIMARY controller first; if that fails, it will proceed to try its SECONDARY, and then its TERTIARY.
    *Finally, if all else fails, an AP will resort to choosing the least loaded AP-Manager interface from all controllers that have responded to it.
  21. 21Join Phase - Join REQUEST The LWAPP join request sent by the AP includes:-The type of controller and its MAC address that it would like to associate with.
    -The AP's hardware and software version, its name and the number and type of radios present on the request-issuing AP
    -The AP's X.509 certificate that's used to initiate a secure LWAPP connection
  22. 22Join Phase - Join REPLY After receiving a join request from an AP, the controller will send a join REPLY that includes:-A result code that either a 0 for success or a 1 for failure. If there's a failure, a status message will indicate why.
    -The controller's X.509 certificate.
    -A test payload to check for the support of jumbo frames.
    *If all goes well, the AP will move on to either the IMAGE DATA STATE to download code or to the CONFIG STATE to download its configuration. If the AP and the WLC are unable to create the trusted relationship required, the AP will transition back to the discovery state and start over.
  23. 23If the code version on the AP isn't in sync with the code on the WLC, the AP enters the:Image Data State, which doesn't always mean its code will be upgraded, because if the WLC's version is lower than the AP's, the AP will downgrade its code version to sync with the WLC's version.
    *Once downloaded, it will be executed by the AP, followed by a reboot. The Discovery and Join phases then repeate, but much faster because the AP will retain the address of the WLC in flash memory.
  24. 24So, finally, now that the AP and the WLC code match, the IMAGE DATA state is complete, and the AP will then begin the:Config State.
    This is where the AP downloads its CONFIGURATION from the WLC and is initiated with a configuration request from the AP that includes the parameters it needs to set and its current values (probably 0)
  25. 25Redundancy (AP) RF LevelIf one AP is lost, the WLC will raise the power levels of neighboring APs to cover the hole.
    Power level 1 is the highest and equals the highest level allowed in the country in which the AP is operating.
    Each level down decreases the power by 50%, so to go from power level 1 to 3 would be a 6dB difference.
    For this to work well, your AP's can't be set to the highest power level for normal coverage or it will clearly be impossible to go to a higher level when necessary. For this reason, I recommend leaving 2 available higher power levels on each AP. But understand that this will require more AP's to cover the same area, something that CISCO is okay with.
  26. 26Redundancy (AP) Port LevelThis refers to using multiple AP-Managers or link aggregation groups on the controller. Device level-multiple WLCs can be configured to provide backup to each other, somewhat like clustering servers for fault tolerance.
  27. 27Redundancy (AP) Port Level N + 1 SolutionOne WLC used as backup.
    All of the APs would have this backup device configured as secondary on their lists of available controllers.
    In the list on each AP, the primary would be its local WLC and the secondary would be the redundant controller. This allows the redundant WLC to provide backup to multiple local WLCs.
  28. 28Redundancy (AP) Port Level N + N SolutionThis solution doesn't require a passive WLC. In this solution, live WLCs are set to back each other up if a failure occurs.
    There are two important considerations when using this solution:
    1) make sure the normal load is balanced between the two.
    2) for this arrangement to work, each WLC should only be operating at or near half capacity during normal operation.
    This way either one will be able to handle the load of the other if it fails.
    To make this work, just set all APs to use the local WLC as primary and the other as secondary. This is the most common configuration.
  29. 29Redundancy (AP) Port Level N + N + 1 SolutionThis solution looks and is configured a lot like N+1 with one more level of safety.
    Again, the WLCs are set to back each other up as in N+1, but you also have a THIRD WLC in the mix that's not active as tertiary.
  30. 30AP MODESThe mode of an AP describes the task that it's fulfilling.
    As with all other settings when using lightweight APs, this is carried out in the controller per AP.
  31. 31The six AP modes are:Local
    Monitor
    Sniffer
    Rouge Detection
    H-REAP
    Bridge
  32. 32Local ModeNormal operation.
    AP performs data transfer for clients and monitors all channels.
  33. 33Monitor ModeAP allows only monitoring and no regular client services.
  34. 34Sniffer ModeAllows AP to capture all frames on a specific channel and sends the frames to a station running an analyzer (OmniPeek, AirMagnet, Wireshark etc.)
  35. 35Rogue Detection ModeAP operates on the wired side without the radio.
    Should be connected to a trunk where it can hear all VLANs.
  36. 36Stations are not allowed to associate with AP if it the AP is in any one of these modes:-Monitor
    -Rogue
    -Sniffer
  37. 37H-REAP ModeHybrid Remote-EDGE Access Point
    Used when the AP is placed in a remote location via a WAN link but positioned where it doesn't warrant an onsite WLC.
    Unlike normal mode, an AP in H-REAP can lose contact with WLC and still function.
    *An important point to remember is that an AP in H-REAP mode can't use Layer 2 or 3 broadcasts to lcate its WLC. It must use DHCP OPTION 43, DNS/DHCP, or OAP via an AP that's already connected to the controller.
  38. 38Bridge ModeEnables AP to be used a bridge in a point-to-point or point-to-multipoint link.
    These kinds of APs function well for mesh networking solutions- since some APs in this type of design don't have a wired connection, bridge moe allows them to use Adaptive Wireless Path Protocol (AWPP)
  39. 39Mobility GroupA set of WLCs that have been grouped together to enhance roaming capability.
    WLCs in the same mobility group can exchange information about their associated clients, and you can take this to the next level by organizing mobility groups in to mobility domains.
    *Keep in mind, clients can only roam between mobility groups in the same mobility DOMAIN.
    If they are not in the same mobility group/domain the re-authentication process has to happen before clients can enter any new mobility group.
  40. 40Intra-Controller RoamingWhen Layer 2 roaming occurs on the same subnet, the client will attempt reauthentication with the new AP and its request will be sent back to its old controller.
    *If the AP has previously met the controller and has the AP in memory, this process takes less than 10ms and is called INTRACONTROLLER Roaming
  41. 41Inter-Controller RoamingIf it's a controller that happens to be a stranger to the AP, the controller involved will then exchange information that effectively moves the client AP.
    This process takes less than 20ms and is called INTERCONTROLLER Roaming
  42. 42RRMRadio Resource Management
    RRM can perform:
    -Channel Assignment
    -Power-Level Control Radio Resource Monitoring
    -Client and Network Load Balancing
    -Dynamic Channel Assignment
    -Coverage Hole Detection & Correction
    -Dynamic Transmit Power Control
    -Interference Detection
    -Avoidance

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2 WIRELESS Karteikarten am LESSON 7 - WIRELESS, erstellt von michael.0lsn am 21/03/2016.
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