Network Utility

A number of tools built into each operating system can be used for diagnostic purpose. These network utilities can help diagnose from where the problems are originating when users have trouble connecting to a network. It may be necessary to utilize the network utilities such as ping command, tracert command, nslookup command etc to help identify and fix network related problems. The ping command is one of the most useful commands which sends a series packets to another system which in turn sends back reply. This utility can be extremely useful in troubleshooting problems with remote hosts. ARP (Address Resolution Protocol) command resolves the IP address to a network card address (MAC address). The ipconfig command allows you to view TCP/IP settings and configuration. The tracert command is the route tracing utility which can be used to determine the path that an IP packet has taken to reach a destination. The netstat command displays protocol information and connection status and provides useful information regarding traffic flow. The nslookup command can be used to query Internet domain servers. In this lesson, you will learn the syntax and functions of these commands in detail.

Troubleshooting Methodology

In spite of monitoring and maintenance, network problem still occurs. When the problem occur network administrator or support engineers can determine and resolve the problem more efficiently by using structured approach rather than using random solution.

The structure approach consists of four steps which will help to solve the problems.

1. Set the problems priority.
2. Divide the network into parts.
3. Develop a list of possible causes.
4. Study the result of the test to identify a solution.

Setting priority Initial step an administrator should take after receiving multiple problems is to establish the priority according to the requirement. Setting priorities in network problem solving is done by assessing the problem’s impact. This can be done by gathering information which provides the foundation for isolating the problem. Information gathering involves scanning the network checking for the cause and a possible solution. This quick scan should also include a review of the history if the problem has occurred before and if there is a recorded solution.

Divide the network into parts If the scan does not gives any solution to the problem, then administrator has to divide the network into as many as segments as possible so that they can troubleshoot a small segment rather than one large network. After isolating the problem down to a specific segment, the administrator can check each network component which includes clients, adapters, hubs, cabling and servers.

Possible Causes After collecting all the information, develop a list of possible causes for the problem. Assign rank in order of most likely to cause the problem to least likely to cause the problem. Select the one from the list of possible causes, test it and check if that is a problem.

Study the result If the test resolves the problem, then it means that you are successful in identifying the problem. If the testing did not isolate the problem, go back to the list of possible solution and try to resolve again.

TCP/IP Network Diagnostic Utilities

The TCP/IP suite has wide variety of programs available for troubleshooting or obtaining performance data. Most of these utilities are command-line programs. To run them, first run cmd.exe (on NT or windows 2000) or command.com (on windows 9x) and when the command prompt box opens, type the desired command line utility.

Ping command

Ping (packet InterNet Groper) command can be used to verify connectivity between computers in a network. The ping command tells the minimum, maximum and average time taken by ping packet to reach the specified destination and how long it will take to receive a reply. Ping is a utility used to verify if a network data packet is capable of being delivered to an address without errors. If errors are found during the delivery of packets to the destination, the ping command displays error message. Ping command creates an echo request to a host on a TCP/IP based network. It communicates by using ICMP (Internet Control Messaging Protocol) protocol. When using ping command, systems sends ICMP packet and waits for a response from a remote host.

Example of ping command: to use ping command, type PING followed by the IP address for which you want to verify the connection at the command prompt.

C :/> ping 192.168.1.2

ARP Command

ARP is used to perform IP address resolution for mapping a 32-bit internet protocol address to MAC address that is recognized in the local network. ARP uses a broadcast to perform this by asking the host which has given IP address to respond to the broadcast with its MAC address.

ARP commands: The arp command has three useful options for trouble shooting which are shown below in the table.

arp
arp -s adds static address that remain until the machine is rebooted
arp -a ( or -g ) displays the IP and MAC address and inform you as to whether the mapping is static or dynamic
arp -d manually delete the entry

With these options you can view the contents of the ARP table, delete a problem entity and install a corrected entry.

The physical address as shown as above in the format 00-25-5e-93-bf-29 is the unique manufacturer identification number.

Note: If an IP address is assigned to particular network adapter, it cannot be changed to a new address. To use ARP, type ARP at the command prompt or type arp /? To view the list of options.

IPCONIG Command

IPCONIG is a MS-DOS command which can be used to display the network settings currently assigned and given by a network administrator. Use ipconfig command to view host computer configuration information including IP address, subnet mask and default gateway. You can use the ipconfig command with all option to view detailed configuration information for all interfaces.

Example: The example below shows the output obtained by entering ipconfig/all

TRACERT Command

TRACERT is short for trace route which displays the path that data takes to reach the destination. The tracert command is used to see the network packet sent and received and the number of hops required for that packet to reach its destination. The tracert command displays a series of routers used for delivering packets from computer to the destination and time taken on each hop. If the packets are unable to be delivered to the destination, the tracert command displays the last router which has successfully forwarded the packet. To use tracert command, type TRACERT and IP address, or the name of the router which you want to see at the command prompt. You can see that there will be a maximum of 30 hops displayed.

NETSTAT Command

The netstat command is used to view the active TCP and UDP port activity for either servers or workstations. When netstat is used with-I flag, netstat displays statistics for the network interface configured. If the- a option is used, it gives all interfaces present not only those that has been configured currently.

To use NETSTAT command, type NETSTAT with the appropriate switches at the command prompt. As with other command-line utilities, use “/? Switch to obtain the list of valid switches and explanation of their function.

Syntax for netstat command

C :/> Netstat /?

NSLOOKUP (Name Server Lookup)Command

NSLOOKUP is a MS-DOS utility which enables to look up an IP address of a domain to host on a network. Using NSLOOKUP, you can identify domain’s name server, IP address of specific host, look up the fully-qualified domain name for an IP address, look up mail server for a specific domain or host etc. If you enter a domain name then you will get IP address to which it corresponds and if you enter an IP number then you get the domain name to which it corresponds. Example is as shown below.