Upon completion of this chapter, you will be able to answer the following questions:
• What network utilities can you use to troubleshoot networks?
There are no key terms for this chapter.
Kishori tries to reach a website using her desktop computer at her nursing station. She gets an error message when trying to reach the site. She checks the wired connection, and it is fine. She uses her laptop to try to reach that same website with no success. On the desktop, she goes to the command prompt and pings a different website on the internet. Now she realizes she has no connection. She calls the IT department. Madhav comes to the station to further investigate the issue. Madhav pings a website. Kishori explains that she tried that already. Then he pings the default gateway and receives a reply. The router is working. It is the ISP that is down. Madhav is impressed that Kishori has learned so much over the past few months. He tells her that she should apply for that promotion and that she can use him as a reference!
Are you ready to learn some troubleshooting commands? Keep reading!
Troubleshooting Commands (17.1)
A number of software utility programs are available that can help identify network problems.
Overview of Troubleshooting Commands (17.1.1)
A number of software utility programs are available that can help identify network problems. Most of these utilities are provided by the operating system as command line interface (CLI) commands. The syntax for the commands may vary between operating systems.
Some of the available utilities include:
• ipconfig – Displays IP configuration information.
• ping – Tests connections to other IP hosts.
• netstat – Displays network connections.
• tracert – Displays the route taken to the destination.
• nslookup – Directly queries the name server for information on a destination domain.
When a device does not get an IP address, or has an incorrect IP configuration, it cannot communicate on the network or access the internet. On Windows devices, you can view the IP configuration information with the ipconfig command at the command prompt. The ipconfig command has several options that are helpful including /all, /release, and /renew.
The ipconfig command (Example 17-1) is used to display the current IP configuration information for a host. Issuing this command from the command prompt will display the basic configuration information including IP address, subnet mask, and default gateway.
The command ipconfig /all (Example 17-2) displays additional information including the MAC address, IP addresses of the default gateway, and the DNS servers. It also indicates if DHCP is enabled, the DHCP server address, and lease information.
How can this utility assist in the troubleshooting process? Without an appropriate IP configuration, a host cannot participate in communications on a network. If the host does not know the location of the DNS servers, it cannot translate names into IP addresses.
If IP addressing information is assigned dynamically, the command ipconfig /release (Example 17-3) will release the current DHCP bindings. ipconfig /renew will request fresh configuration information from the DHCP server. A host may contain faulty or outdated IP configuration information and a simple renewal of this information is all that is required to regain connectivity.
If, after releasing the IP configuration, the host is unable to obtain fresh information from the DHCP server, it could be that there is no network connectivity. Verify that the NIC has an illuminated link light, indicating that it has a physical connection to the network. If this does not solve the problem, it may be an issue with the DHCP server or network connections to the DCHP server.
Packet Tracer – Use the ipconfig Command (17.1.3)
In this activity, you will use the ipconfig command to identify incorrect configuration on a PC.
Refer to the online course to complete this Packet Tracer.