CCDA 640-864 Summary Notes – Chapter 5 – Day 10

Exam Topic 2 – Part 1: Cisco Unified Wireless Network (UWN) Architecture

Benefits:

• Deliivers scalable, manageable and secure WLANs
• Combines wired and wireless network
• Reduced Total Cost of Ownership (TCO)
• Enhanced visibility and control
• Dynamic RF management
• WLAN Security
• Mobility
• Enhanced productivity and collaboration

Network Elements:

• Client devices
• access points – access to the network
• network unification – controllers
• network management – Wireless Control System (WCS)
• mobility services like guest access, location services, voice and thread detection

LWAPP (Lightweight Access Point Protocol)

• IETF Standard RFC draft
• Controls setup, authentication and operation between contoller and AP
• Uses AES for authentication and encryption between AP and Controller
• Messages can be transported in bothL2 andL3 tunnels
  • L2LWAPP Tunnels
    • First method
    • APs did not need IP
    • WLC needed to be in every subnet in  which the APs resided
    • LWAPP uses EtherType code 0xBBBB
    • Deprecated
  • L3 LWAPP Tunnels
    • Prefered
    • Messages from the WLC  use UDP ports 12222 for control and 12223 for data messages
    • Used between the LWAP and WLC
    • WLC does not need to reside in the same segment as APs
    • Transport modes:
      • L2
        • LWAPP uses proprietary code to communicate with AP
      • L3
        • LWAPP uses IP to communicate with AP 
        • IP collected from DHCP server
        • DHCP server a must

CAPWAP (Control and Provisioning for Wireless Access Point)

• IETF Standard
• Controls setup, authentication and operation between contoller and AP
• Uses Datagram Transport Layer Security (DTLS) for authentication and encryption between AP andController
• Has a Dynamic maximum transmission unit (MTU) discovery mechanism
• From the Controller :UDP port 5246 for control messages and 5247 for data messages
• From the AP: ephemeral (short time) UDP Port thats from a hash between the AP MAC
• Uses L2 Tunnel between the LWAP and WLC
• APs get IP via DHCP

Cisco Unified Wireless Network Split-MAC Architecture

• Control and data messages are split
• APs communicate withWLC using control messages over wired network
  • With a WLC, the AP uses a CAPWAP tunnel to the WLC. The WLC has a 802.1Q trunk to the LAN switch (data vlan, voice vlan and management vlan )
• Data messages are encapsulated and forwarded to and from wireless clients
• LWAP MAc Functions:
  • 802.11: Beacon probe response
  • 802.11 Control: Packet acknowledgment and transmission
  • 802.11e (QoS): Frame queuing and packet prioritization
  • 802.11i (security): MAC layer data encryption/decryption
• WLC MAC Functions
  • 802.11 MAC Management: Association requests and actions
  • 802.11e Resource Reservation: Reserve resources for applications
  • 802.11i (security): Authentication and key management

Local MAC

• Moves MAC management from WLC to AP
• Supported by CAPWAP
• Allows termination of client traffic at the wired port of AP
  • Refered to as autonomous AP
  • Autonomous AP acts as a 802.1q translational bridge with a trunk to the LAN switch (data vlan, voice vlan and management vlan )
• LWAP MAc Functions:
  • 802.11: Beacon probe response
  • 802.11 Control: Packet acknowledgment and transmission
  • 802.11e (QoS): Frame queuing and packet prioritization
  • 802.11i (security): MAC layer data encryption/decryption
  • 802.11 MAC Management: Association requests and actions

• WLC MAC Functions
  • 802.11: Proxy association requests
  • 802.11e Resource Reservation: Reserve resources for applications
  • 802.11i (security): Authentication and key management

AP Modes:

• Local Mode
  • Default
  • AP measures noise floor and interference and scans for IDS threats @ 180 seconds for a duration of 60 ms
  • Scanning occures in unused channels
• Hybrid Remote Edge AP (H-REAP) mode
  • LWAP can reside across a WAN link and communicate with WLC
  • Allows local MAC
  • Supported: 1130, 1140, 1240AB, and 1250AG series
• Monitor Mode:
  • CAPWAP APs can exclude themselves form handling data traffic
  • APs act as  dedicated sensors for location based services, rogue AP detection  and IDS
  • AP cannot serve clients
  • AP continupously cycles through all configured channels listening for approx 60ms
• Rogue detector (RD) mode
  • Monitor rogueAPs
    • RD sees all VLANS in network
    • RD is connected to a trunk port
    • LAN switch sends all the rogue AP / client MAC to RD
    • RD sends the MACs to WLC to compare the MACs with the ones that the WLC APs has heard
    • If match, WLC knows that the rogue AP where the clients are connected  is in the wired network
  • APs do not transmit or contain rogue APs
• Sniffer mode
  • CAPWAP functions as sniffer. Captures and forwards all packets on a particular channel to a remote machine runningAeroPeek (third party network analyzer software)
    • Aeropeek supports decoding of data packets
  • Can only be enabled if running aeropeek
• Bridge mode
  • Provides for high bandwidth bridging connectivity
  • Supported:
    • point-to-point bridging
    • point-to-multipoint bridging
    • point-to-point wireless access with integrated wireless backhaul
    • point-to-multipoint wireless access with integrated wireless backhaul.