Windows 7 : Troubleshooting Common Problems on Small Networks

2/28/2011 11:13:20 AM
The first step to learning about troubleshooting falls into the theoretical arena with the OSI model. See this table for a list of the OSI model layers and their names. The OSI model helps us break networks into different layers in terms of how they correspond to the different applications and protocols we use to transmit data. Each protocol works in different ways, and the OSI model helps us understand how they function and what they do.

1. Using the Network Diagnostics and Repair Option

Windows 7 offers the ability to self-diagnose network connectivity problems using Windows Network Diagnostics. This feature can help to identify problems with network adapters and TCP/IP issues. If you do not have a cable properly connecting the adapter to the network, it will also notify you of this problem. The wizard goes through a simple set of tests to determine the problem, alleviating the need to complete these tasks manually. However, if the wizard cannot fix the problem, you must determine the problem yourself, as discussed in the other troubleshooting sections of this chapter.

You can diagnose and repair network problems by completing these steps:

  1. Click Start, and then click Control Panel.

  2. In the Control Panel, click Network and Internet→Network and Sharing Center.

  3. In the Network and Sharing Center, click “Change adapter settings.” This opens the Network Connections window.

  4. Right-click the network connection you want to troubleshoot and then select Diagnose.

  5. When Windows Network Diagnostics finishes testing your network configuration, you’ll see a list of possible solutions, as shown in Figure 1. Follow the instructions provided to try to correct the problem, or click a solution to have Windows Network Diagnostics perform a troubleshooting task for you.

Figure 1. Diagnosing your networking problem

2. Checking Physical Connectivity

Using the functionality of the OSI model, you can identify where protocols function to aid in troubleshooting network problems. If you are unable to connect to a network, you should begin at the layer 1 level. This layer tells you to look specifically at the physical connectivity of your computer to the network. Identifying whether your cabling works correctly should be the first step of network troubleshooting. You can usually verify that you have connectivity by making sure that the link light is lit on the network adapter. Usually if your link light is lit and the activity light is showing activity by flashing, you can assume the computer has connectivity. With wireless routers, you can go a step further by logging in to the router and confirming whether the device shows up as being currently connected.

If you complete the troubleshooting steps in the section but you still have issues connecting to the network properly, replace the network cable or check the wireless configuration settings. If you have doubts as to whether you have connectivity with Ethernet, take a few minutes to replace the network cable, as it is easy and inexpensive to replace this piece of equipment. Telltale signs that you need to replace your cable include no link light when connected to a powered-on network device, and the fact that you can either only send or only receive data.

If you have verified that you have connectivity, you must determine whether the network adapter exists within Device Manager on your computer. If your computer sees the network adapter, verify that you have the latest driver installed. Sometimes you can have problems with network functionality due to an old device driver associated with the network adapter. This scenario can happen after a software update to the operating system and when a third-party application makes changes to a shared control file, or to a file the driver relies upon for quality communications.

If you still cannot connect to the network, check your TCP/IP configuration settings. You can also use the techniques discussed in the upcoming sections Section 3 and Section 4 to help you with troubleshooting configuration issues. If none of these efforts resolves the problem, try replacing the network adapter with a second network adapter. This should verify connectivity problems or resolve the issue. If the problem follows the adapter, you can assume the adapter has a problem. If you still cannot connect to the network with a new adapter, verify that the slot in the motherboard works correctly. If your network adapters are integrated into the motherboard, you can still add a different physical network adapter into a slot on the motherboard. You may then want to disable the integrated adapters in firmware to avoid IRQ conflicts on your computer.

To check the functionality of the slot in the motherboard, install the network adapter into a different slot on the motherboard. If you still cannot connect to the network or see an adapter, you should update firmware on your motherboard or contact the manufacturer’s technical support to either identify the problem with the board or get a replacement board, assuming you have warranty support on the board in question. Once you have the replacement board, you can connect the network adapter to verify connectivity.

3. Using the Command Line to Diagnose Network Problems

Microsoft offers many different tools to help diagnose network problems. The best tools for testing your network are those available at the command line. For troubleshooting, be sure to start the command line with elevated privileges by completing the following steps:

  1. Click Start, click All Programs, and then click Accessories.

  2. Right-click Command Prompt and then select “Run as administrator.”

  3. This opens an administrator command prompt that you can use to perform any necessary troubleshooting procedures.

To begin troubleshooting, you should first determine the IP configuration for all network adapters on your computer. To accomplish this task, type IPconfig /all at the command prompt you opened previously. You will see the output of the TCP/IP stack as well as some physical details concerning the characteristics of your local machine, similar to Example 1, which gives you a great view of the properties controlling access to your network and its resources. You can see immediately the name of the host, type of connection, routing capability, DNS name, MAC address, IP address, DHCP server IP address, subnet, default gateway, and IP address for each adapter connected to the computer.

Example 1. IPConfig /all output
C:\>IPconfig /all
Windows IP Configuration
Host Name . . . . . . . . . . . . : RC1-5600
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . :

Wireless LAN adapter Wireless Network Connection:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Broadcom 802.11g Network Adapter
Physical Address. . . . . . . . . : 00-14-A5-A0-15-F1
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes

Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek RTL8139/810x Fast Ethernet NIC
Physical Address. . . . . . . . . : 00-16-36-46-FF-15
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::2da2:3d:9f2e:297c%10(Preferred)
IPv4 Address. . . . . . . . . . . :
Subnet Mask . . . . . . . . . . . :
Lease Obtained. . . . . . . . . . : Tuesday, October 12, 2009 2:02:32 PM
Lease Expires . . . . . . . . . . : Wednesday, October 13, 2009 2:35:32 PM
Default Gateway . . . . . . . . . :
DHCP Server . . . . . . . . . . . :
DHCPv6 IAID . . . . . . . . . . . : 234886710
DNS Servers . . . . . . . . . . . :
NetBIOS over Tcpip. . . . . . . . : Enabled

The first setting you need to verify is the IP address of the computer. If you are using DHCP on a network device, make sure you see DHCP Enabled. . . . . : Yes in the output of the IPCONFIG /ALL command. If you see this setting, verify that you have received an IP address. If you do not have an IP address, check whether you can see an address for the DHCP server. When identifying the IP address, if you see either or 169.265.X.X as an IP address, you did not connect to the DHCP server. You can try to reapply for an IP address by typing the IPconfig /renew command at the command line. If this fails to give you an IP address, try inputting a static IP address within the subnet of the DHCP server to see if you can gain access to the network . If you can, make sure the DHCP server is running correctly. Alternatively, simply unplug and then plug in the device to force it to reset itself.

Windows offers a host of commands for testing your network, but by far the king of all commands is ping. Pinging allows you to direct specific-size packets at a computer to verify connectivity. Ping actually echoes back with information on the connectivity to another computer. If you wanted to verify your ability to send packets, you should first ping your computer on the local loopback address, The loopback address provides a simple mechanism for testing the Windows network stack.

Next, proceed to verify that name resolution is working correctly. You can accomplish this task by pinging the name of a computer on the Internet, such as a website. If you are unable to ping the computers on the Internet, check the TCP/IP settings of the network adapter to verify that you have enabled the TCP/IP protocol. See Example 2 for examples of how to ping different network hosts by name or IP address.

Example 2. Ping command

Pinging with 32 bytes of data:

Reply from bytes=32 time<1ms TTL=128
Reply from bytes=32 time<1ms TTL=128
Reply from bytes=32 time<1ms TTL=128
Reply from bytes=32 time<1ms TTL=128

Ping statistics for
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milliseconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms


Pinging [] with 32 bytes of data:

Reply from bytes=32 time=52ms TTL=235
Reply from bytes=32 time=75ms TTL=235
Reply from bytes=32 time=51ms TTL=235
Reply from bytes=32 time=52ms TTL=235

Ping statistics for
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milliseconds:
Minimum = 51ms, Maximum = 75ms, Average = 57ms

If you cannot receive packets by pinging another computer, you should proceed to ping the IP address of your default gateway. You can find the IP address of your default gateway in the output of the IPconfig /all command.

If you are unable to ping your default gateway, either contact your network administrator or check the gateway. In most instances, your gateway consists of a broadband router or similar device, and you should check the device for proper functionality. You can identify errors with packets on the device by looking for status lights identifying packet collisions or another error. Try resetting the device by unplugging it, waiting a few seconds, and powering it on again. Alternatively, if the device has a Reset button, you can press this button as well. If this process does not work, you may need to update firmware on or replace the network device. If your default gateway consists of a cable modem or DSL router, contact your service provider for steps to alleviate your problem.

If you can ping your default gateway but are unable to connect to the Internet and you are using a network router or other personally managed network device for a gateway, check the cable going to your outside provider. You should also try to ping outside your internal network to test for outside connectivity. If you can successfully ping an external IP address your gateway should be in good shape. If you can ping by IP address externally but not to a name, such as, you need to verify that you have input the IP address of your DNS server properly in the TCP/IP configuration. With DHCP, the network device usually provides the DNS server address, so you would need to check the configuration of the device. If you verify these settings but still cannot connect to the Internet, use the NSLookup command to check for DNS resolution. See Example 3 for an example of how to use the NSLookup command.

Example 3. NSLookup output
Default Server:



To verify DNS resolution for connectivity to the Internet or possibly your Active Directory domain, type NSLookup at the command line. You should receive a > prompt. Type the name of the domain to which you want to connect and press the Enter key. If you receive output showing the IP addresses of the domain, your resolution works correctly. If you receive output that says something like “Non-Existent” domain, you should try another DNS server for output or contact your ISP to find out why its DNS server fails queries.

If you can query the DNS name correctly but are still having problems with Internet connectivity, use the tracetrt command to check the routing device hops between yourself and the desired location. At the command line, you can accomplish this task by typing:

tracert <Destination IP or Name>

You will see a maximum of 30 hops to the destination, including an IP address, and possibly the name of the device. If you see timeouts or other error messages for addresses outside your network, there are problems outside of your control. You should contact your service provider to determine whether it is aware of these problems and is working to correct them.

4. Fixing Network Problems

TCP/IP networking has many different facets, and additional protocols that ride on top of it. Although it is the single most prolific technology in use today, there are inherent problems with some implementations. Use Table 1 to help diagnose common problems with network connectivity or protocol issues.

Table 1. Troubleshooting matrix
No IP AddressCheck DHCP scope on the router or server. Input a static IP address.
Cannot Ping MachinePing <Host Name>. Ping <Default Gateway>.
Cannot Ping that the TCP/IP protocols are enabled on the adapter. Verify that the adapter is enabled in Device Manager.
Cannot Ping Default GatewayVerify that the gateway has network connectivity.

Check the cables connecting your computer to the network device.

Reset the network device by powering it off and then powering it on.

Contact your ISP.

Replace the network device.
Cannot Reach InternetCheck gateway connectivity using TRACERT <IP Destination>.

Verify DNS resolution using NSLookup.

Input DNS server addresses as part of the network device DHCP configuration.

Input DNS server addresses in the TCP/IP properties of the network adapter.
No Network ConnectivityFor Ethernet, check the cable connecting the network adapter to the network.

For wireless, reorient antenna, relocate router, or try a different channel.

Check Link/Activity status on the adapter.

Update the network adapter driver.

Flash firmware on motherboard (integrated adapters only).

Move the network adapter to a different slot on the motherboard.

Replace the network adapter.
Only Send or Receive PacketsFor Ethernet, reseat the network cable or replace the network cable. For wireless, reorient antennae, relocate router, or try a different channel.

  •  Windows 7 : Advanced Networking Concepts
  •  Windows 7 : Networking with TCP/IP (part 2) - Understanding IPv6 & Configuring IPv4, IPv6, and Other Protocols
  •  Windows 7 : Networking with TCP/IP (part 1) - Understanding IPv4 & Using Private IPv4 Addresses and Networking Protocols
  •  Windows 7 : Mapping Your Networking Infrastructure (part 2) - Viewing the Network Map & Viewing and Managing Your Network Connections
  •  Windows 7 : Mapping Your Networking Infrastructure (part 1) - Using the Network and Sharing Center
  •  Windows 7 : Understanding Home and Small-Business Networks
  •  Troubleshooting Windows 7 Programs and Features
  •  Windows 7 : Getting Help and Giving Others Assistance
  •  Windows 7 : Recovering After a Crash or Other Problem (part 3)
  •  Windows 7 : Recovering After a Crash or Other Problem (part 2) - Restoring Previous Versions of Files & Recovering Files from Backup
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