Testing and Troubleshooting Networks Chapter 19 Release 1672009

Testing and Troubleshooting Networks Chapter 19 Release 16/7/2009 Jetking Infotrain Ltd.

Chapter Objectives n n Identify the tools used for troubleshooting physical networks Perform crimp testing and router testing Perform loop back test Use the diagnostic utilities Release 16/7/2009 Jetking Infotrain Ltd.

Recall n n n n Threats are of two types: Internal and External Firewall protects the system from unauthorized access of resources Firewalls are of two types: Packet – Filter and Proxy Digital signature is an authentication technique Encryption is conversion of a plain text document into a encrypted form It is used to provide security to data RAID is a collection of hard disks to share and replicate data Release 16/7/2009 Jetking Infotrain Ltd.

Network troubleshooting Tools n The various tools available for checking the network are: q q q Software Tools Hardware Tools Touchy Tools Release 16/7/2009 Jetking Infotrain Ltd.

Loopback Test n n n Signal is transmitted and it echos back Echo signal compared with original signal Tests the transmission path and tools used for transmission Traces a faulty node in network Requires a loopback plug Chapter 16/7/2009 Release 4 Jetking Infotrain Ltd. 5

Network Monitors n Detect and display problems present in the network n Provides data related to network traffic n Analyze data traffic to determine various network problems that can occur Release 16/7/2009 Jetking Infotrain Ltd.

LAN Tester - I n n Used to test 10, 100 and 1000 Base-T Networks Consists of two units q Main unit n n q Indicates LAN device type i. e hub, switch Determines speed of LAN and type of link Remote Probe n Chapter 16/7/2009 Release 4 Used to locate faults in a cable Jetking Infotrain Ltd. 7

LAN Tester - II n Functions of LAN tester q q Verify PC to hub speed and data transmission Check hub to hub data transmission Determines any speed bottlenecks present on 10 and 100 Base-T LANs Continuously tracks LAN link Release 16/7/2009 Jetking Infotrain Ltd.

Cable Testers and Certifiers n n n Checks electrical connections Determines if a short or open circuit is present in the network Consists of a source of current, volt meter and microcontroller Release 16/7/2009 Jetking Infotrain Ltd.

Time-Domain Reflectometers n n n Locates fault in metallic cables Transmits a pulse through the cable At every discontinuity, an echo is reflected back Used to test long cables Results are displayed on a CRT or LCD Release 16/7/2009 Jetking Infotrain Ltd.

Protocol Analyzers - I n It may be a software or hardware device n n Captures packets from network Analyzes captured packets Analyzes the network traffic Identifies bottlenecks in network Operate on network layer Identifies active systems on network n Removes the faulty system from network n n Release 16/7/2009 Jetking Infotrain Ltd.

Protocol Analyzers - II Types of protocol analyzers q Packet analyzer Capture packets present on the wire and store them for analyzing later n Does a statistical analysis of the data captured but it is not its primary function n q Statistical analyzers Gather quantitative data to prepare a report on the different statistical trends n Does not store the packets for later analysis n Release 16/7/2009 Jetking Infotrain Ltd.

Touchy Tools n n Used to identify network problems Problems are identified using asking various questions to user Analyzes current situation and compares it with set of baselines Adequate knowledge and experience is useful to determine problems Release 16/7/2009 Jetking Infotrain Ltd.

Backups n n Used to preserves a copy of original files Should be performed on regular basis Useful when a data loss occurs Restores system to previous state Release 16/7/2009 Jetking Infotrain Ltd.

Baselines n n n Used to compare the system’s current performance with reference level set by the network administrator Determines possible network problems Performance monitor helps to set baselines Monitors both real time as well as historical data Baselines may change with time Release 16/7/2009 Jetking Infotrain Ltd.

Troubleshooting Model - I n Steps of troubleshooting model q q Establish the symptoms Isolate the cause of the problem Establish what has changed that might have caused the problem Ask Isolating questions Release 16/7/2009 Jetking Infotrain Ltd.

Troubleshooting Model - II q q q Identify the most probable cause Implement a solution Test the solution Recognize the potential effects of the solution Document the solution Release 16/7/2009 Jetking Infotrain Ltd.

Four layer Model n Four layers model q Hardware – Considers all the hardware related issues n q Protocols – Deals with problems related to protocols n q Checks the installation and configuration of protocols Network – Considers the client and server concept n q Focuses on problems with network devices such as hubs, switches Determines which node will act as client and which will act as server Shared Resources – Determines which resources are to be shared Release 16/7/2009 Jetking Infotrain Ltd.

Cable Testing and Certification - I n Cable Distance q q n Measures the distance of a cable and helps to locate the point where a short or open is present Speed of pulse depends on wires, type of insulation and external shielding Wire Map q q q Used for twisted-pair installations Detects split pairs Detects crossed pair condition Release 16/7/2009 Jetking Infotrain Ltd.

Cable Testing and Certification - II n Attenuation q q n Reduction in strength of signal Cable Testers are used to measures loss of power Near-End Crosstalk q q Transfer of electricity from one wire to another in the same cable Causes n n Untwisted patch cables Crossed pairs Release 16/7/2009 Jetking Infotrain Ltd.

Cable Testing and Certification III n Network Monitoring and Protocol Decoding q Cable checkers monitor network traffic n q n Locates loose cables Noise-Level Test q q n Detects high or low level traffic External signal that interfere with original signals Measured in millivolts (m. V) Testing Fiber q Fiber-optic cable testers use optical time-domain reflectometer which depend on the reflection of light Release 16/7/2009 Jetking Infotrain Ltd.

SNMP n n n Simple Network Management Protocol Networking standard protocol Used with TCP/IP networks Monitors and manages the network Helps to examine network performance Detect network faults or inappropriate access Release 16/7/2009 Jetking Infotrain Ltd.

Potential Network connectivity problem n Causes of network connectivity problems q q q q Incorrect network adapters (NIC) Incorrect switch settings Faulty hardware Driver issues Upgradation of operating system Server relocation The network adapter is incompatible with the motherboard Release 16/7/2009 Jetking Infotrain Ltd.

Network Workstation Troubleshooting Process n Steps to troubleshoot networkstation q q Determine what stopped working Determine if failure is on a single user’s workstation Try to log onto the network Check the NIC’s link light Release 16/7/2009 Jetking Infotrain Ltd.

Case Study - I In the Money. Maker bank a new computer is connected in the Customer Service department of Chennai branch. The computer is connected to the local network. But it is unable to connect to the Internet. Chapter 16/7/2009 Release 4 Jetking Infotrain Ltd. 25

Problem Unable to connect computer to the Internet Release 16/7/2009 Jetking Infotrain Ltd.

Suggested Solution Add the new DNS address provided by the network administrator in the DNS server box Release 16/7/2009 Jetking Infotrain Ltd.

Netstat Command n n n Displays TCP/IP information Determines which ports are active Identifies ports that are vulnerable to attacks Provides connection details Provides data about TCP and UDP Release 16/7/2009 Jetking Infotrain Ltd.

Ipconfig Command n n n Displays all network settings Identifies DHCP problems Used with windows 2000 and later versions Displays and resets DNS cache Sets and displays DHCP class IDs for an adapter Release 16/7/2009 Jetking Infotrain Ltd.

Winipcfg Command n n n Provides IP addressing details Used for windows 98 or earlier versions Provides details such as IP address, Subnet Mask, Default Gateway, DHCP Server, WINS Server, etc. Release 16/7/2009 Jetking Infotrain Ltd.

ARP Command n n Links IP address of a node with its hardware address Various ARP command options can be used to display or change the values in ARP table Release 16/7/2009 Jetking Infotrain Ltd.

Nbtstat Command n n n Resolves Net. BIOS name resolution problems Used when WINS server is not accessible displays protocol information and current TCP/IP connection using Net. BIOS over TCP/IP (NBT) Release 16/7/2009 Jetking Infotrain Ltd.

Route Command n n Allows you to view and make changes in the IP routing table Used to differentiate between routes to hosts and routes to networks by reading the network address of the destination Release 16/7/2009 Jetking Infotrain Ltd.

Case Study - II The employees of Money. Maker bank have been constantly complaining that they are not able to get connected to a particular device. To check the problem, John who is the network administrator of the branch performs a ping test. While performing the ping test he gets Request timed out error Chapter 16/7/2009 Release 4 Jetking Infotrain Ltd. 34

Problem Pinging to a device gives “request time out” error Chapter 16/7/2009 Release 4 Jetking Infotrain Ltd. 35

Suggested Solution n n Ping to the loop back address or do a self ping Ping to the gateway If you get a “destination host unreachable” error message then gateway address in TCP/IP is not configured properly Ping to the device If you are still getting the “request time out” error then the device is either shut down or not working properly Chapter 16/7/2009 Release 4 Jetking Infotrain Ltd. 36

Summary - I n n Loopback test is used to test if the ports are functioning properly Cross over cables temporarily connect devices when router, switch or hub is not present Faults in cables like twisted wire pairs, coaxial cables can be located using time-domain reflectometer Network monitor provides information related to network traffic. Release 16/7/2009 Jetking Infotrain Ltd.

Summary - II n n Protocol analyzers perform the function of interpreting the contents of the packets that are intercepted Ping, tracert, netstat, ipconfig, and winipcfg are some commands that can be used to troubleshoot various network problems Netstat is used to check the ports that are active on your system Ipconfig provides information related to TCP/IP connection Release 16/7/2009 Jetking Infotrain Ltd.

Summary - III n n n Ipconfig is used for Windows 2000 or later versions Winipcfg is used for windows 98 or other versions ARP links IP address of node to its physical address Release 16/7/2009 Jetking Infotrain Ltd.