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84 Cards in this Set
- Front
- Back
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All wireless devices operate in the radio waves range of the |
electromagnetic spectrum. |
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Wi-Fi systems are |
half-duplex. |
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Wi-Fi systems can |
transmit and receive on the same radio channel, not simultaneously. |
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Distributed Coordination Function (DCF) is a |
collision avoidance mechanism used for Wi-Fi systems. |
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(DCF) ensures clients only transmit if the channel is |
clear. |
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Wireless clients and Access Points use the |
RTS and CTS control frames to facilitate the actual data transfer. |
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Wireless three-stage process: |
Discover new wireless AP. Authenticate with AP. Associate with AP. |
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Modes Of Discovering APs: |
Passive mode Active mode |
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Passive mode - The AP openly advertises its service by periodically sending |
broadcast beacon frames. |
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Broadcast beacon frames include: |
SSID supported standards security settings. |
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Active mode - The wireless client initiates the process by broadcasting a |
probe request frame. |
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Probe request frame includes: |
SSID supported standards |
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The response frame from the AP provides the |
security settings. |
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Authentication types: |
Open authentication Shared key authentication |
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Open authentication is a |
free pass to wireless network. |
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Shared key authentication technique is based on a key that is |
pre-shared between the client and the AP. |
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Shared key authentication process: |
Client authentication request. AP Challenge. Client encypts with key. AP decrypts the key. Authenticates if keys match. |
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After a wireless client has been authenticated, the AP proceeds to the |
association stage. |
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The wireless client forwards an Association Request frame that includes its |
MAC address. |
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The AP responds with an Associate Response that includes the AP BSSID, which is the |
AP MAC address. |
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The AP maps a logical port known as the association identifier (AID) to the |
wireless client. |
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It is the responsibility of the International Telecommunication Union - Radiocommunication Sector (ITU-R) to |
regulate the allocation of the radio frequency (RF) spectrum. |
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The radio waves range is subdivided into |
radio frequencies. microwave frequencies. |
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WLANs connect clients to the network through a wireless |
access point (AP) or wireless router. |
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Wireless LAN devices have transmitters and receivers tuned to specific |
frequencies of the radio waves range. |
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Ranges of frequencies are called |
bands. |
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Benefits of Wireless: |
Increased flexibility increased productivity reduced costs ability to grow and adapt |
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Wireless Technologies: |
Wireless Personal-Area Networks (WPAN) Wireless LANs (WLANs) Wireless Wide-Area Networks (WWANs) |
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Bluetooth |
IEEE 802.15 WPAN standard, distances up to 100m. |
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Wi-Fi (wireless fidelity) |
IEEE 802.11 WLAN standard, distances up to 300m. |
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WiMAX (Worldwide Interoperability for Microwave Access) |
IEEE 802.16 WWAN standard, access of up to 30 miles (50 km). |
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Cellular broadband uses service provider cellular access to provide |
mobile connectivity. |
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Satelite broadband provides network access to remote sites through the use of a |
directional satellite dish. |
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2.4 GHz (UHF) |
802.11b/g/n/ad |
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5 GHz (SHF) |
802.11a/n/ac/ad |
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60 GHz (EHF) |
802.11ad |
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802.11n can also use |
channel bonding. |
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Channel bonding combines |
two 20 MHz channel into one 40 MHz channel. |
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The three organizations influencing WLAN standards are: |
IEEE ITU-R Wi-Fi Alliance |
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IEEE |
Specifies how RF is modulated to carry information. |
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ITU-R |
Regulates the allocation of the RF spectrum and satellite orbits. |
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Wi-Fi Alliance |
promotes the growth and acceptance of WLANs. |
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Wireless clients use their wireless NIC to discover nearby APs advertising their |
SSID. |
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Clients then attempt to |
associate and authenticate with an AP. |
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Access Points can be categorized as either |
autonomous APs or controller-based APs. |
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Autonomous APs are useful in situations where only a |
couple of APs are required in the network. |
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Autonomous APs are configured and managed |
individually. (Unless clustered) |
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Single Point Setup (SPS) is a form of clustering that makes autonomous AP deployment |
easier and faster. |
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Cluster Conditions: |
Cluster mode enabled. Matching cluster name. Same network segment. Same radio mode. |
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Controller-based APs are useful in situations where |
many APs are required in the network. |
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Controller-based APs require no |
initial configuration. |
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Controller-based are managed centrally from a controller in the |
cloud. |
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The controller pushes management settings to the AP, such as |
firmware updates security settings wireless network SSIDs settings |
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The Cisco Meraki cloud architecture is a management solution used to |
simplify the wireless deployment. |
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Most business class APs require the use of |
external antennas. |
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IEEE 802.11n/ac/ad use MIMO technology to |
increase available bandwidth. |
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MIMO uses multiple antennas to |
exchange more data. |
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Wireless Topology Modes: |
Ad hoc mode Infrastructure mode |
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Ad hoc mode |
when two wireless devices communicate without using APs or wireless routers. |
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Infrastructure mode |
clients interconnect via a wireless router or AP. |
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Basic Service Set (BSS) - consists of a single AP interconnecting |
all associated wireless clients. |
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Extended Service Set (ESS) |
two or more BSSs joined through a common distribution system (DS). |
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If the demand for a specific channel is too high, that channel is likely to become |
oversaturated. |
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The saturation of the wireless medium degrades the |
quality of the communication. |
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Direct-sequence spread spectrum (DSSS) - is designed to spread a signal over a |
larger frequency band. |
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The signal is multiplied by a “crafted noise” known as a |
spreading code. |
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Frequency-hopping spread spectrum (FHSS) transmits radio signals by |
by rapidly switching a carrier signal. |
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Orthogonal frequency-division multiplexing (OFDM) - a single channel utilizes |
multiple sub-channels on adjacent frequencies. |
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A best practice for WLANs requiring multiple APs is to |
use non-overlapping channels. |
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Wireless Threats: |
Wireless intruders Rogue APs Interception of data DoS attacks |
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A rogue AP is an AP or wireless router that has either been connected to a corporate network without explicit |
authorization and against corporate policy. |
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A rogue AP is an AP or wireless router that has been connected or enabled by an attacker to capture |
client data. |
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A rogue AP is an AP or wireless router that has been connected or enabled by an attacker to gain access to |
network resources, or to launch man-in-the-middle attack. |
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Wireless DoS attacks can be the result of: |
Improperly configured devices. intentionally interference Accidental interference |
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Types of DoS attacks: |
A spoofed disconnect attack. A CTS flood. |
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To mitigate many of these attacks, Cisco has developed a variety of solutions, including |
the Cisco Management Frame Protection (MFP) feature |
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To address the threats of keeping wireless intruders out and protecting data, two early security features were used: |
SSID cloaking MAC addresses filtering |
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Shared Key Authentication Methods: |
Wired Equivalent Privacy (WEP) Wi-Fi Protected Access (WPA) (TKIP) IEEE 802.11i/WPA2 (AES) |
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The IEEE 802.11i and the Wi-Fi Alliance WPA and WPA2 standards use the following encryption protocols: |
Temporal Key Integrity Protocol (TKIP) Advanced Encryption Standard (AES) |
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Temporal Key Integrity Protocol (TKIP) |
used by WPA. |
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Advanced Encryption Standard (AES) |
used by WPA2. |
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WPA and WPA2 support two types of authentication: |
Personal - home or small office Enterprise - Intended for enterprise networks |
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These fields are necessary to supply the AP with the required information to contact the AAA server: |
RADIUS Server IP address RADIUS port numbers Shared key |
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Troubleshooting When the Network Is Slow: |
Upgrade your wireless clients Split the traffic |
