CCRI J. Bernardini 1 Chapter 11 Network Settings and Wireless LAN Troubleshooting (Modified) CCRI ENGR 1500

CWNA Guide to Wireless LANs, Second Edition Chapter Eleven Network Settings and Wireless LAN Troubleshooting (Modified)

CWNA Guide to Wireless LANs, Second Edition 3 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 Edition 4 Ethernet Parameters: Basic Settings Figure 11-1: Basic Ethernet settings

CWNA Guide to Wireless LANs, Second Edition 5 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 Edition 6 Ethernet Parameters: Advanced Settings Figure 11-2: Advanced DNS settings

CWNA Guide to Wireless LANs, Second Edition 7 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 Edition 8 Ethernet Parameters: Advanced Settings (continued) Figure 11-3: Advanced Ethernet settings

CWNA Guide to Wireless LANs, Second Edition 9 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 Edition 10 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 Edition 11 Mobile IP Settings Most WLAN implementations follow standard IP address plan –Single subnet for entire WLAN –Subnet: Portion of network that shares a common address component Subnetting WLANs creates problems for users who roam between WLAN subnets –Cannot roam into new subnet without changing IP address –Need mechanism to ensure a device configured with specific IP address can continue to communicate when entering new subnet

CWNA Guide to Wireless LANs, Second Edition 12 Mobile IP Settings (continued) Figure 11-4: Roaming between wireless subnets Mobile IP will be covered in another set of slides

CWNA Guide to Wireless LANs, Second Edition 13 Troubleshooting Wireless Networks Troubleshooting can be difficult with WLANs –Many factors can impact wireless transmissions Many of them are “non-technical” –Technology is relatively new –Problems can be result of anything from overlooking check box on a dialog box to metal objects in path of RF signal Categorized into identifying and solving problems with RF transmissions, APs, and wireless devices

CWNA Guide to Wireless LANs, Second Edition 14 Solving RF Transmission Near/Far Problem Two steps to identify device that is a victim of near/far transmission problem Wireless protocol analyzer running on a device displays signal strength Low signal strength may indicate problem May not indicate near/far problem Also determine signal strength on nearby devices Possible Solutions Move device with stronger transmission power farther away from AP Reduce transmission power of devices closer to AP Increase transmission power of devices farther away from AP Netstubler- measure signal strength

CWNA Guide to Wireless LANs, Second Edition 15 Solving RF All-Band Interference Problems FHSS uses range of frequencies that change during transmission –Bluetooth operates in same 2.4 GHz ISM band as IEEE b/gWLANs Can create all-band interference –IEEE b/g and Bluetooth devices do not “peacefully coexist” in same environment Proposed Options for b/g and Bluetooth “ –Change the RF spectrum, Modify power levels –Add switching software, Change the MAC layer, Change PHY layer Best solutions is to not use the two devices together or migrate to a wireless technology

CWNA Guide to Wireless LANs, Second Edition 16 Solving System Throughput Problems Many factors influence WLAN transmission speed: –AP processor speed –Distance from AP –Implementing security solutions –Number of users associated with an AP –Packet size –RTS/CTS protocol To troubleshoot: –Determine if all devices experiencing problem or only a single device –Identify potential causes that may have least impact on system if changed Qcheck - Free tool for Throughput testing –Install on end points

17 Solving RF Transmission Problems: Co-Location Throughput Possible Solutions: -Change channels to Channels 1 and 11 -Migrate to a 8 non-overlapping channels

18 Solving RF Transmission Problems: Co-Location Throughput (continued)

CWNA Guide to Wireless LANs, Second Edition 19 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 All Aps have different test sequences Cisco, Linksys, Belkin, Netgear are all different

CWNA Guide to Wireless LANs, Second Edition 20 Solving Access Point Problems 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 Edition 21 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 Edition 22 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 Edition 23 Solving Wireless Device Problems: Troubleshooting Wireless Devices Possible causes if problems makings connection: –Incompatible IEEE 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 Edition 24 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 Edition 25 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

CCRI J. Bernardini 26 Mobile IP Components MN – Mobile Node (VMD) FA – Foreign Agent (MAP) HA – Home Agent (MAP) AAP – Authoritative Access Point MAP – Mobile IP Access Point (MN) VMD – Visiting Mobile Device (MN) COA – Care-of-Address HAN – Home Agent Network FAN – Foreign Agent Network CN – Correspondent Node

CCRI J. Bernardini 27 Subnets and Mobile IP Subnets provide many advantages: –make network management easier –Subnets reduce broadcasts –Subnets provide security –Subnets use subnet masks ( ) WLAN subnets creates problems for roaming devices Example: – /24 can seamlessly roam within x /24 –Note /24 is a subnet mask – /24 can not seamlessly roam within x /24 without changing the IP address Mobile IP offers a solution – can roam as a “guest” on the x network

CCRI J. Bernardini 28 Mobile IP Devices Visiting Device –Some APs support Mobile IP and Visiting devices Mobile IP Access Point –Performs all Mobile IP services Home Agent –Visiting devices home router –Tunnels packets from “visited” network to “visiting” device Authoritative Access Point (AAP) –Uses a subnet map to track all home “visiting” devices Foreign Agent –A router the is the attachment point for “visiting” devices –Tunnels packets to the Home Agent for the “visiting” device

CCRI J. Bernardini 29 Mobile IP Process - Discovery 1- Mobile Node (MN) gets address from Home Agent (HA) 2- MN moves to Foreign Agent (FA ) network 3- MN discovers FA or solicits for an agent. 4- MN gets Care-of-Address (COA) from FA Mobile IP 3-Step Process 1-Discovery 2-Registration 3-Tunneling MN – Mobile Node FA – Foreign Agent HA – Home Agent

CCRI J. Bernardini 30 Mobile IP Process - Registration 5- MN send registration request to FA 6- FA checks request, adds MN to pending list 7- FA relays request to HA 8- HA checks request and creates a mobile binding 9- HA sends registration reply to FA 5 Mobile IP 3-Step Process 1-Discovery 2-Registration 3-Tunneling FA checks reply and adds MN to visitor list and relays reply to MN 11-FA creates a routing entry and tunnel to HA 12- MN check reply and creates a tunnel to the HA Through the FA MN – Mobile Node FA – Foreign Agent HA – Home Agent CN – Correspondent Node

CCRI J. Bernardini 31 Mobile IP- Tunneling and Packet Forwarding MN – Mobile Node FA – Foreign Agent HA – Home Agent CN – Correspondent Node COA- Care-of-Address Correspondent Node (CN) sends packet to MN and is routed to HA 14- HA intercepts packets and tunnels to the FA using the COA 15- FA relays the packets to the MN 14 15

CCRI J. Bernardini 32 Mobile Node Movement

Wireless Test Equipment and White Papers Many companies supply wireless test equipment –Cisco –Fluke –Ixia –Others See List of White Papers relating to Wireless testing CCRI J. Bernardini 33

CWNA Guide to Wireless LANs, Second Edition 34 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 Edition 35 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 WLANs that use the same frequency spectrum Co-location throughput can affect the performance of access points that use b/g technology because of channel overlap on channels 1, 6, 11

CWNA Guide to Wireless LANs, Second Edition 36 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