This is a comprehensive guide for using the tools that are built into Windows when you are trying to determine the cause of TCP/IP networking problems. This article lists recommendations for using these tools to diagnose network problems. Although this list is not complete, the list does provide examples that show how you can use these tools to track down problems on the network.
TCP/IP troubleshooting tools
The following list shows some of the TCP/IP diagnostic tools that are included with Windows XP:
• Network Diagnostics in Help and Support
Contains detailed information about the network configuration and the results of automated tests.
• Network Connections folder
Contains information and configuration for all network connections on the computer. To locate the Network Connections folder, click Start, click Control Panel, and then click Network and Internet Connections.
• IPConfig command
Displays current TCP/IP network configuration values, updates, or releases, Dynamic Host Configuration Protocol (DHCP) allocated leases, and display, register, or flush Domain Name System (DNS) names.
• Ping command
Sends ICMP Echo Request messages to verify that TCP/IP is configured correctly and that a TCP/IP host is available.
• Hostname command
Displays the name of the host computer.
• Nbtstat command
Displays the status of current NetBIOS over TCP/IP connections, updates the NetBIOS name cache, and displays the registered names and scope ID.
• PathPing command
Displays a path of a TCP/IP host and packet losses at each router along the way.
• Route command
Displays the IP routing table and adds or deletes IP routes.
• Tracert command
Displays the path of a TCP/IP host.
To view the correct command syntax to use with each of these tools, type -? at a command prompt after the name of the tool.
Windows XP Professional tools
Windows XP Professional contains the following additional tools: • Event viewer
Records system errors and events.
• Computer Management
Changes network interface drivers and other components.
The procedure that you use to troubleshoot TCP/IP issues depends on the type of network connection that you are using and the connectivity problem that you are experiencing.
For most issues that involve Internet connectivity, start by using the Network Diagnostics tool to identify the source of the issue. To use Network Diagnostics, follow these steps: 1. Click Start, and then click Help and Support.
2. Click the link to Use Tools to view your computer information and diagnose problems, and then click Network Diagnostics in the list on the left.
3. When you click Scan your system, Network Diagnostics gathers configuration information and performs automated troubleshooting of the network connection.
4. When the process is completed, look for any items that are marked “FAILED” in red, expand those categories, and then view the additional details about what the testing showed.
You can either use that information to resolve the issue or you can provide the information to a network support professional for help. If you compare the tests that failed with the documentation in the Manual Troubleshooting section later in this article, you may be able to determine the source of the issue. To interpret the results for TCP/IP, expand the Network Adapters section of the results, and then expand the network adapter that failed the testing.
You can also start the Network Diagnostics interface directly by using the following command:
netsh diag gui
To manually troubleshoot your TCP/IP connectivity, use the following methods in the order that they appear:
Method 1: Use the IPConfig tool to verify the configuration
To use the IPConfig tool to verify the TCP/IP configuration on the computer that is experiencing the problem, click Start, click Run, and then type cmd. You can now use the ipconfig command to determine the host computer configuration information, including the IP address, the subnet mask, and the default gateway.
The /all parameter for IPConfig generates a detailed configuration report for all interfaces, including any remote access adapters. You can redirect IPConfig output to a file to paste the output into other documents. To do this, type:
ipconfig > \folder_name\file_name
The output receives the specified file name and is stored in the specified folder.
You can review the IPConfig output to identify issues that exist in the computer network configuration. For example, if a computer is manually configured with an IP address that duplicates an existing IP address that is already detected, the subnet mask appears as 0.0.0.0.
If your local IP address is returned as 169.254.y.z with a subnet mask of 255.255.0.0, the IP address was assigned by the Automatic Private IP Addressing (APIPA) feature of Windows XP Professional. This assignment means that TCP/IP is configured for automatic configuration, that no DHCP server was found, and that no alternative configuration is specified. This configuration has no default gateway for the interface.
If your local IP address is returned as 0.0.0.0, the DHCP Media Sensing feature override turned on because the network adapter detected its lack of connection to a network, or TCP/IP detected an IP address that duplicates a manually configured IP address.
If you do not identify any issues in the TCP/IP configuration, go to Method 2.
Method 2: Use the Ping tool to test your connectivity
If you do not identify any issues in the TCP/IP configuration, determine whether the computer can connect to other host computers on the TCP/IP network. To do this, use the Ping tool.
The Ping tool helps you verify IP-level connectivity. The ping command sends an ICMP Echo Request message to a destination host. Use Ping whenever you want to verify that a host computer can send IP packets to a destination host. You can also use Ping to isolate network hardware problems and incompatible configurations.
Note If you ran the ipconfig /all command, and the IP configuration appeared, you do not have to ping the loopback address and your own IP address. IPConfig has already performed these tasks to display the configuration. When you troubleshoot, verify that a route exists between the local computer and a network host. To do this, use the following command:
ping IP address
NoteIP address is the IP address of the network host that you want to connect to.
To use the ping command, follow these steps: 1. Ping the loopback address to verify that TCP/IP is installed and correctly configured on the local computer. To do this, type the following command:
If the loopback test fails, the IP stack is not responding. This problem may occur if any one or more of the following conditions is true: • The TCP drivers are corrupted.
• The network adapter is not working.
• Another service is interfering with IP.
2. Ping the IP address of the local computer to verify that the computer was correctly added to the network. If the routing table is correct, this procedure just forwards the packet to the loopback address of 127.0.0.1. To do this, type the following command:
ping IP address of local host
If the loopback test succeeds but you cannot ping the local IP address, there may be an issue with the routing table or with the network adapter driver.
3. Ping the IP address of the default gateway to verify that the default gateway is working and that you can communicate with a local host on the local network. To do this, type the following command:
ping IP address of default gateway
If the ping fails, you may have an issue with the network adapter, the router or gateway device, the cabling, or other connectivity hardware.
4. Ping the IP address of a remote host to verify that you can communicate through a router. To do this, type the following command:
ping IP address of remote host
If the ping fails, the remote host may not be responding, or there may be a problem with the network hardware between computers. To rule out an unresponsive remote host, use Ping again to a different remote host.
5. Ping the host name of a remote host to verify that you can resolve a remote host name. To do this, type the following command:
ping Host name of remote host
Ping uses name resolution to resolve a computer name into an IP address. Therefore, if you successfully ping an IP address but you cannot ping a computer name, there is a problem with host name resolution, not with network connectivity. Verify that DNS server addresses are configured for the computer, either manually in the properties of TCP/IP, or by automatic assignment. If DNS server addresses are listed when you type the ipconfig /all command, try to ping the server addresses to make sure that they are accessible.
If you cannot use Ping successfully at any point, verify the following configurations: • Make sure that the local computer’s IP address is valid and that it is correct on the General tab of the Internet Protocol (TCP/IP) Properties dialog box or when it is used with the Ipconfig tool.
• Make sure that a default gateway is configured and that the link between the host and the default gateway is working. For troubleshooting purposes, make sure that only one default gateway is configured. Although you can configure more than one default gateway, gateways after the first gateway are used only if the IP stack determines that the original gateway is not working. The purpose of troubleshooting is to determine the status of the first configured gateway. Therefore, you can delete all the other gateways to simplify your task.
• Make sure that Internet Protocol security (IPSec) is not turned on. Depending on the IPSec policy, Ping packets may be blocked or may require security. For more information about IPSec, go to Method 7: Verify Internet Protocol security (IPSec).
Important If the remote computer that you are pinging is across a high-delay link such as a satellite link, response may take longer. You can use the -w (wait) parameter to specify a longer timeout period than the default timeout of four seconds.
Method 3: Use the PathPing tool to verify a route
The PathPing tool detects packet loss over multiple-hop paths. Run a PathPing analysis to a remote host to verify that the routers on the way to the destination are operating correctly. To do this, type the following command:
pathping IP address of remote host
Method 4: Use the Arp tool to clear the ARP cache
If you can ping both the loopback address (127.0.0.1) and your IP address but you cannot ping any other IP addresses, use the Arp tool to clear out the Address Resolution Protocol (ARP) cache. To view the cache entries, type any one of the following commands:
To delete the entries, type the following command:
arp -d IP address