© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE I Chapter 6 1 Configure a Wireless Router Chapter 7

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 2 Objectives  Describe the components and operations of basic wireless LAN topologies.  Describe the components and operations of basic wireless LAN security.  Configure and verify basic wireless LAN access.  Configure and troubleshoot wireless client access.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 3 Why Wireless?  Mobility  Less expensive implementation  FLEXIBILITY

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 4 Why Wireless?  Mobility  Less expensive implementation  FLEXIBILITY Better productivity More relaxed employees Better resutls Increased profits

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© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 6 WLAN / LAN Comparison Characteristic Wireless LAN802.3 Ethernet LAN Physical LayerRadio Frequency (RF)Cable Media AccessCollision AvoidanceCollision Detection AvailabilityAnyone with radio NIC in range of AP Cable connection required Signal interferenceYESInconsequential RegulationAdditional regulation by authorities IEEE standard dictates

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 7 RF Characteristics  RF does not have boundaries  RF unprotected from outside signals  RF signal weakens with distance  RF subject to additional and different regulations than wired LANs

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 8 Adding Wireless LAN Components  Extends a Ethernet LAN infrastructure  Wireless clients connect through a wireless router or access point (AP)  Wireless adapter in client communicates with wireless router or AP using RF signals  Once connected, wireless clients can access network resources just as if they were wired to the network

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 9 Wireless LAN Standards a802.11b802.11g802.11n Band5.7 GHz2.4 GHz ChannelsUp to 2333 ModulationOFDMDSSSDSSS/OFDM Data Rates<= 54 Mbps<=11 Mbps<=11 / <=54 Range150 ft (35 m) Release DateOct 1999 Jun 2003 Pros Fast, less prone to interference Low cost, good range Fast, good range, not easily obstructed Cons Higher cost, shorter range Slow, prone to interference Prone to Interference from appliances

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 10 Wireless LAN Standards a802.11b802.11g802.11n Band5.7 GHz2.4 GHz 2.4 / 5 GHz ChannelsUp to 2333 ModulationOFDMDSSSDSSS/OFDMMIMO-OFDM Data Rates<= 54 Mbps<=11 Mbps<=11 / <=54 ? 248 Mbps for 2 MIMO streams Range150 ft (35 m) 230 ft (70 m) Release DateOct 1999 Jun 2003? 2008 Pros Fast, less prone to interference Low cost, good range Fast, good range, not easily obstructed Very good data rates, improved range Cons Higher cost, shorter range Slow, prone to interference Prone to Interference from appliances ?

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 11 IMPORTANT!  RF bands allocated by ITU-R  ITU-R designates 900 MHz, 2.4 GHz, 5 GHz as unlicensed for ISM communities  RF globally unlicensed but subject to local regulations  In US, FCC administers use of RF bands  In Europe, ETSI administers us of RF bands  This impacts selection of wireless components

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 12 Wi-Fi Alliance, ITU-R, IEEE Roles  Wi-Fi Alliance, ITU-R, & IEEE influence WLAN standards  ITU-R regulates allocation of RF bands  IEEE specifies how RF is modulated to carry information  Wi-Fi ensures vendors make interoperable devices  Wi-Fi Alliance ( provides Wi-Fi certificationwww.wi-fi.org

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter based wireless infrastructure

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 14 Wireless Access Points  Wireless clients do not typically communicate directly— they communicate through an AP.  AP converts frame to frame  AP is a layer 2 device-functions like a hub since RF is a shared medium and all radio traffic is ‘heard’  AP oversees CSMA/CA

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 15 CSMA/CA (Carrie Sense Multiple Access /Collsion Avoidance)  AP oversees CSMA/CA  WLAN devices sense the medium for RF energy  If certain threshold of RF energy, then wait till free  If free, then send  When AP receives data from client, AP sends ‘ack’ so client will not retransmit

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 16 The Hidden Node Problem  If clients (nodes) are at the maximum range from the AP, they may be too distant from each other to be detected and transmit simultaneously.  The distant node transmission are subject to attenuation.  One resolution: CSMA/CA feature RTS/CTS  RTS/CTS-request to send/clear to send  When enabled, AP allocates the medium

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 17 Wireless Security Threats  WLAN access: in range of access point/credentials  Unauthorized Access: in range and ‘cracking’ techniques  3 Major Categories of Threat War Drivers Hackers (Crackers) Employees  Rogue APs Unauthorized-interferes with normal operation

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 18 Wireless Security Threats (2)  Man-in-the-Middle Attacks (MITM) Host selected as target Hacker uses packet-sniffing software (Wireshark) to observe client connecting to AP-may read/copy username, server name, IP addresses, ID to compute response, challenge/associate response (clear text) All users in BSS may be compromised! To defeat MITM: authenticate users on your WLAN, monitor devices and traffic, IPS (Intrusion Prevention System)

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 19 Wireless Security Threats (3)  Denial of Service (DoS) b/g use the unlicensed 2.4 GHz ISM band 1.Common consumer products may interfere causing DoS 2.Attacker use wireless NIC for AP-floods BSS with CTS, defeating the CSMA/CA (constant stream of collisions) 3.Attacker sends disassociate commands & clients disconnect Clients then immediately try to reassociate, which creates a burst of traffic. Attacker sends another disassociate command and the cycle repeats itself.

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© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 24 Configure a wireless NIC

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 25 How to solve access point firmware issues

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 26 How to solve access point firmware issues

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© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 32 Summary  Wireless LANs use standards such as IEEE a IEEE b IEEE g IEEE n  Basic Service set –Mobile clients use a single access point for connectivity  Extended service set –Multiple access point that share an SSID

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 33 Summary  WLAN security practices/methods include –MAC address filtering –SSID making –Implementing WPA2  Configuration of wireless NIC and access point –Configure both of them the same way SSID –Ensure that the latest firmware is installed  Troubleshooting WLANs include doing the following: –Check channel setting –Check for interference

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE 1 Chapter 6 34 END Configuring a Wireless Router Chapter 7