CWNA guide to wireless LANs 2nd ch11

CWNA Guide to Wireless LANs, Second Edition Chapter Eleven Network Settings and Wireless LAN Troubleshooting Objectives • Explain the wired network settings that can be modified in a wireless network • List troubleshooting techniques for solving RF transmission problems • Describe how to solve access point problems • Describe the types of wireless device problems and explain how to solve them CWNA Guide to Wireless LANs, Second Edit Wired Network Settings for Wireless Networks • All APs have RJ-45 connector that allows them to connect to an Ethernet hub or switch – Provide wired network resources to wireless devices – Settings for connecting to Ethernet network occasionally need to be adjusted • To improve wireless performance or provide additional capabilities • Mobile IP parameters can be set on APs CWNA Guide to Wireless LANs, Second Edit Ethernet Parameters: Basic Settings Figure 11-1: Basic Ethernet settings CWNA Guide to Wireless LANs, Second Edit Ethernet Parameters: Basic Settings (continued) • Allow wireless network administrators to designate Ethernet port as primary port of the AP – Select whether port “adopts” identity of primary port Table 11-1: Ethernet identification CWNA Guide to Wireless LANs, Second Edit Ethernet Parameters: Advanced Settings Figure 11-2: Advanced DNS settings CWNA Guide to Wireless LANs, Second Edit Ethernet Parameters: Advanced Settings (continued) • Setting on Figure 11-2: – Default Domain: Name of network’s IP domain – Current Domain: Domain that is serving the AP – IP addresses of up to three DNS servers can be entered under Domain Name Servers – Domain Suffix: Last portion of domain name of current network domain CWNA Guide to Wireless LANs, Second Edit Ethernet Parameters: Advanced Settings (continued) Figure 11-3: Advanced Ethernet settings CWNA Guide to Wireless LANs, Second Edit Ethernet Parameters: Filtering • Allows control of types of network traffic that pass from wired Ethernet network to WLAN devices – Configure AP to act as type of firewall • Different types of filtering: – Some devices filter at high level and can block an application from being requested – Other filtering can reject request for specific IP port – At the lowest level, filtering can look at received frames and block based on type of frame CWNA Guide to Wireless LANs, Second Edit Ethernet Parameters: Filtering (continued) • Frames can be filtered by protocol used – e.g., TCP, UDP, IPX • Frames can be filtered by frame format – Four-character hexadecimal number found in each frame that indicates protocol and frame format Table 11-2: Frame formats CWNA Guide to Wireless LANs, Second Edit 10 Solving RF Transmission Problems: Co-Location Throughput (continued) Figure 11-8: Adjacent Channels and CWNA Guide to Wireless LANs, Second Edit 27 Solving RF Transmission Problems: Co-Location Throughput (continued) • Possible solutions: – Change channels to Channels and 11 – Migrate to 802.11a • non-overlapping channels CWNA Guide to Wireless LANs, Second Edit 28 Solving RF Transmission Problems: Co-Location Throughput (continued) Figure 11-9: Separate channels CWNA Guide to Wireless LANs, Second Edit 29 Solving Access Point Problems • All APs have external light emitting diodes – Ethernet indicator: Signals traffic on wired LAN • Green when Ethernet cable is connected • Blinks green when packet received or transmitted • Off when Ethernet cable not connected – Status indicator: Signals operational status • Green indicates AP associated with at least one wireless device, • Blinking green means AP operating normally but is not associated with any wireless devices – Radio indicator: Blinks green to indicate RF activity CWNA Guide to Wireless LANs, Second Edit 30 Solving Access Point Problems (continued) Table 11-4: Cisco Aironet LED information CWNA Guide to Wireless LANs, Second Edit 31 Solving Access Point Problems (continued) Table 11-4 (continued): Cisco Aironet LED information CWNA Guide to Wireless LANs, Second Edit 32 Solving Access Point Problems (continued) • If AP does not communicate with devices, check: – SSID – WEP keys – Security settings • In extreme circumstances, may be necessary to delete current AP configuration and return all settings to factory defaults CWNA Guide to Wireless LANs, Second Edit 33 Solving Wireless Device Problems: Wireless Device Connection Process • Five-step connection process: – Scan for access points • Wireless network adapter sends series of Probe Request frames • APs within range respond with Beacon frame that contains the capabilities of the wireless AP – Choose an access point • Decision based on: – Wireless AP capabilities – SSID matches a preferred network – Signal strength CWNA Guide to Wireless LANs, Second Edit 34 Solving Wireless Device Problems: Wireless Device Connection Process (continued) • Five-step connection process (continued): – Authenticate with the access point • Type of authentication depends on security capabilities of AP and how wireless device has configured to authenticate with AP – Associate with the access point – Obtain an IP address • Manual addressing • DHCP addressing • APIPA addressing CWNA Guide to Wireless LANs, Second Edit 35 Solving Wireless Device Problems: Troubleshooting Wireless Devices • Possible causes if problems makings connection: – Incompatible IEEE 802.11 standards – Mismatched authentication methods – Different WEP keys • Will not prevent association, but will prevent successful communication – Incorrect WEP key order – Mismatched pre-shared key – Conflict between Windows Wireless Auto Configuration and a third-party configuration tool – Incorrect MAC address CWNA Guide to Wireless LANs, Second Edit 36 Solving Wireless Device Problems: Troubleshooting Wireless Devices (continued) • Possible causes if wireless device intermittently disconnects from AP: – Incompatible 802.1x authentication • For computers running Windows XP with SP1, clear Enable IEEE 802.1x authentication for this network check box in Authentication tab – Duplicate SSID • Generally result of default SSID being used on APs – Infection by computer virus • Run antivirus software CWNA Guide to Wireless LANs, Second Edit 37 Solving Wireless Device Problems: Troubleshooting Wireless Devices (continued) • Possible causes if wireless device intermittently disconnects from AP (continued): – Faulty hardware • Run diagnostic tests for AP or wireless network adapter • Use current drivers – Wireless attacks • May require special scanners to pinpoint attacker – Device misconfiguration CWNA Guide to Wireless LANs, Second Edit 38 Summary • Maintaining a wireless LAN involves adjusting the wired Ethernet settings to ensure peak performance • Most WLAN network implementations follow the standard Internet protocol (IP) address plan, which calls for a single subnet to be used for the entire WLAN • Mobile IP provides users the freedom to roam beyond their home subnets while still maintaining their home IP addresses CWNA Guide to Wireless LANs, Second Edit 39 Summary (continued) • A device that is transmitting at higher signal strength and is located closer to the access point will drown out a weaker signal from a device that is farther away and is using less power • Technologies such as Bluetooth which use the entire 2.4 GHz spectrum can impact IEEE 802.11 WLANs that use the same frequency spectrum • Co-location throughput can affect the performance of access points that use 802.11b/g technology because of channel overlap on channels 1, 6, 11 CWNA Guide to Wireless LANs, Second Edit 40 Summary (continued) • Solving access point problems often starts with observing the LED lights that provide information regarding Ethernet and RF activity along with operational status • Wireless device problems fall into two broad categories: the inability to make a successful wireless connection and intermittently disconnecting from the access point CWNA Guide to Wireless LANs, Second Edit 41 ... continue to communicate when entering new subnet CWNA Guide to Wireless LANs, Second Edit 11 Mobile IP Settings (continued) Figure 11-4: Roaming between wireless subnets CWNA Guide to Wireless LANs, ... placement of wireless devices CWNA Guide to Wireless LANs, Second Edit 19 Solving RF Transmission Problems: Near/Far (continued) Figure 11-7: Signal strength CWNA Guide to Wireless LANs, Second... and explain how to solve them CWNA Guide to Wireless LANs, Second Edit Wired Network Settings for Wireless Networks • All APs have RJ-45 connector that allows them to connect to an Ethernet hub