#mnemonics

• CSMA/CA (Carrier Sense Multi-Access with Collision Avoidance) is used to avoid collisions in wireless networks (like CSMA/CD in wired networks)
• WPA Authentication Modes
  • PSK = Personal
  • 802.1X = Enterprise
• WLC Trivia
  • When creating Interfaces, you first Name the interface, then assign a VLAN ID
  • When mapping a WLAN to a VLAN, you're asked for these properties in order:
    • Type
      • Almost always WLAN
    • Profile Name
      • Used to identify the WLAN on the WLC
      • Usually the same as the SSID
    • SSID
    • ID
      • Unique number that identifies the WLAN in the WLC
      • Specific number or order doesn't matter
      • Automatically increments
  • Enable WPA+WPA2 PSK Authentication
  • 
    • WLAN Tab>Edit WLAN
    • Security Subtab>Layer 2 Subtab
    • Choose WPA+WPA2
    • Check the box for WPA2 Policy
• VLAN QoS
  • Platinum = Voice
  • Gold = Video
  • Silver = Best Effort, default
  • Bronze = Background

Wireless Signal Disruption

• ARRDSI
  • Absorption
    • Signal is absorbed in material and converted to heat
  • Reflection
    • Signal bounces off material
  • Refraction
    • When the wave is broken up because it's slowed down by the medium it's passing through
    • Refraction, literally "to break up"
  • Diffraction
    • When a signal is split around an object, creating a blindspot
    • Diffraction, literally "to break apart"
  • Scattering
    • Physical interference, like dust, smog, uneven surfaces, etc.
  • Interference
    • Signal interference, like other WLAN connections, microwaves, etc.

Wireless Signal Anatomy

• FAPH
  • Amplitude
    • The size of each cycle/oscillation in a wave
  • Period
    • The time it takes for one cycle/oscillation to take place.
    • The Period is the reciprocal of the Frequency
      • Period = 1/frequency
  • Frequency
    • The number of cycles/oscillations per unit of time.
    • The Frequency is the reciprocal of the Period
      • Frequency = 1/period
  • Hertz
    • Cycles per second
      • The unit of measurement for Frequency
    • kHz = 1,000 cycles per second
    • GHz = 1,000,000,000 cycles per second
• In 2.4GHz Wifi, there are 13 (technically 14) channels available
  • Each channel is 22 MHz wide
  • Avoid overlapping channels by choosing channels 1, 6, and 11

Metadata

OSI or TCP/IP Layer

CCNA Exam Topic

#extop-2-9 #extop-2-6

Contributors

Sources