network cisco ccna gns3 certification arteq

network cisco ccna gns3 certification arteq
a network runs through it

Search insearchofthecert

Monday, December 19, 2011



4 agencies

itu-r -  worldwide organization that manages the assignment of freq's

ieee - wireless standardization of wlan 802.11

wi-fi alliance -  industry consortium that encourages interoperability standards through wi-fi
cert program

FCC  - u.s. govt agency that regulates usage of various communication freq's

IEEE introduced wlan standards in 1997 with ratification of 802.11 next came 802.1b then 802.1a
and 802.1g

802.11b is 11 Mbps @ 2.4 Ghz with 11 channels (3 nonoverlapped)
802.11a is 54 Mbps @ 5 Ghz with 23 channels (12 nonoverlapped)
802.11g is 54 Mbps @ 2,4 Ghz with 11 channels (3 non0verlapped)

using DSSS max speed for b and g is 11Mbps (b only uses DSSS)
using OFDM max speed for a and g is 54Mbps (a only uses OFDM)

ranges in feet 802.11a highest throughput 54= distance about 75 ft lowest throughput 6=about 200
                     802.11b                             11                          150                             1            350
                     802.11g                             54                           90-100                       6            300

Ad hoc mode -  one or two or just a few more send wlan frames to each directly for short periods
Infrastructure mode -  through an AP, allows for server and  internet communication

2 submodes BSS and ESS
Basic service set uses a single AP to make a wireless LAN
Extended service set uses more than one AP, with overlapping cells to allow
   for roaming in a larger area

IBSS Independant basic service set 2 devices directly connected-no ap

encoding 3 types
FHSS frequency hopping spread spectrum uses all band freq's, hopping between unlicensed bands
   for consecutive transmissions
DSSS Direct sequence spread spectrum for use with b @ 2.4 Ghz unlicensed band
OFDM Orthogonal frequency division multiplexing (a only @ 2.4 Ghz)

Coverage area quality depends on freq, obstructions, interference, antennae, and dsss and ofdm
    when encoding through the air
    higher freq's send data faster but have smaller coverage

CSMA/CA signals from hosts sharing an AP cannot be isolated from collisions if they transmit at
   the same time

1) listen for busy freq
2) random wait timer before sending a frame to reduce chance for simultaneous sends
does this sound familiar yet?
3) when timer expires, listen again for not busy, resend frame
4) after whole frame sent, listen for acknowledgement
5) no acknowledgement, restart csma logic (step 1)

security risks
war drivers - hacker driving around to exploit insecure or weak ap's (strong authentication)
hackers - find information or deny service, often compromising end hosts as a means to get on
   the enterprise without breaching firewalls (strong encryption, and authentication
employees - who install AP's on the LAN with no security, allowing easy hacker
   access (IDS, IPS and SWAN)
rogue AP's - attacker captures packets, finds service set identifier, then sets up an AP that
   employees might associate with (IDS, IPS and SWAN)

risk reduction - mutual authentication, a secret password key on client and AP
   encryption, key and algorithm to scramble frame contents
   intrusion detection, IDS IPS and Swan (structured wireless aware architecture,
   cisco concept to detect rogues)

WEP Wired equivalency privacy - 1997 original standard provided authentication and encryption
   used static PSK's (pre-share keys) manually configured, easily cracked, only 40 bits

Cisco came up with an interim solution; dynamic keyexchange, new encryption key for each
   packet and user authentication using 802.1x instead of device authentication

WPA Wi-fi protected access - 2003 similar to Cisco interim, dynamic key exchange using TKIP
   (temporal key integrity exchange protocol) uses either 802.1x user authentication or
   device authentication with PSK) the encryption algorithm uses MIC (message integrity

802.11i WPA2 - dynamic key exchange, stronger encryption using AES (advanced encryption standard)
   and user authentication. not backward compatible with wpa or wep

implementation -
   AP parameters include SSID, RF channel and authentication
   Clients are only authentication
   802.11 is by design plug and play because of open authentication, whereas WEP and WPA
      use PSK's that must match exactly

1) verify veracity of existing wired network, connect all ap's in the same
   ESS to the same vlan
2) set up the ap as a switch, because it is a switch. however, use a straight through cable;
   ip address, mask and default-gateway
3) set up the IEEE standard (a,b,g, or combination)
   wireless channel, SSID,power
4) build a client (support the same wlan standard, it will learn the SSID from the AP)
5) verify at client end
6) configure security
7) verify client works with security enabled

i have yuck brain...

No comments:

Post a Comment