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Windows XP

Troubleshooting Network Problems : Repairing a Network Connection

12/2/2011 3:40:05 PM

Checking Connection Status

A good starting point for diagnosing network problems is to check the status of your network connection. This will show you things such as whether you’re connected, your connection speed, your current IP address, your network’s default gateway addresses, DHCP server, DNS server, and so on. Invalid entries for these and other status items could provide a hint as to where the network problem might lie.

To display the connection status, you have two choices:

  • If a connection icon appears in the taskbar’s notification area, double-click the icon.

    Tip

    If no connection icon appears in the taskbar’s notification area, select Start, All Programs, Accessories, Communications, Network Connections. Right-click your network connection and click Properties. In the General tab of the property sheet that appears, activate the Show Icon in Notification Area When Connected check box, and then click OK.


  • In the Network Connections window, double-click the connection.

Figure 1 shows the Status dialog box that appears. In the General tab, there are two groups to check out:

ConnectionThis group shows the connection’s current status: Connected or Disconnected. If the status value shows Connected, the Duration value shows how long the connection has been active, and the Speed value shows the connection speed in Mbps. For a wireless connection, this group also shows the network name and the current signal strength.
ActivityThis group shows the number of network packets that the connection has sent and received. A very low number for either value gives you a hint about the direction of the problem. For example, a very low Sent value might indicate that you are not sharing your resources correctly or at all.

Figure 1. In the Status dialog box, the General tab offers basic connection details and activity metrics.


The Support tab displays basic connection data, including your IP address, subnet mask, and default gateway address, as shown in Figure 2. The Address Type value will be one of the following:

Assigned by DHCPA DHCP server assigns your IP address automatically.
Manually ConfiguredYou entered a static IP address in the Internet Protocol (TCP/IP) Properties dialog box.
Automatic Private AddressYour network uses the Automatic Private Internet Protocol Addressing (APIPA).
Invalid IP AddressAn invalid IP Address (0.0.0.0) usually indicates one of the following problems:
  • Your network’s DHCP server is down.

  • The static IP address you entered conflicts with another IP address on the network.


Figure 2. Use the Support tab to examine connection data such as your IP address, subnet mask, and default gateway address.


For other network connection data, click the Details button to see information such as the addresses of the DHCP server, DNS servers, and WINS server. You can also click Repair to initiate the Windows XP network connection repair utility.

Checking Network Utilization

If your network feels sluggish, it could be the server or node you’re working with is sharing data slowly or that network traffic is exceptionally high. To see whether the latter situation is the cause of the problem, you can check out the current network utilization value, which is the percent of available bandwidth that your network adapter is currently using.

To check network utilization, follow these steps:

1.
Right-click an empty section of the taskbar and then click Task Manager.

2.
Display the Networking tab, shown in Figure 3.

Figure 3. Use Task Manager’s Networking tab to check the current network utilization percentage.


3.
If you have multiple adapters, click the one you want to check in the Adapter Name list.

4.
Use the graph or the Network Utilization column to monitor the current network utilization value.

Repairing a Network Connection

When a user calls Microsoft Support to resolve a networking issue, the support engineer has a list of troubleshooting steps that he takes the user through. For example, if there’s a problem with a DHCP network, the engineer usually starts by telling the user to use IPCONFIG to release (ipconfig /release) and then renew (ipconfig /renew) the IP address. Other steps include running specific commands with the ARP (Address Resolution Protocol) and NBTSTAT (NetBIOS over TCP/IP Statistics) utilities.

Someone at Microsoft realized that all these steps could be automated by creating a script that runs the various ipconfig, arp, and nbtstat commands. The result is the network connection repair tool, which runs the following six troubleshooting steps:

  • Broadcasts a request for the renewal of the computer’s DHCP lease.

    Note

    A DHCP lease is a guarantee that the DHCP client computer will have the IP address supplied by the DHCP server for a specified period of time. To avoid lease expiration, the DHCP client usually sends a request—a DHCPREQUEST message—for lease renewal to the original DHCP server after 50% of the lease time has expired. If 87.5% of its lease time has expired, the DHCP client sends a lease renewal request to all available DHCP servers. This broad request for a lease renewal is what the repair tool does. Why send a DHCPREQUEST message instead of just using IPCONFIG to release and renew the IP address? Because if the current address is functioning properly, releasing that address could cause extra problems if a new address can’t be obtained from a DHCP server. With a lease renewal request, the DHCP client keeps its current address.

  • Flushes the ARP cache—The ARP (Address Resolution Protocol) handles the conversion of an IP address to a physical address of a network adapter. (To see the physical address of your adapter, open the connection’s Status dialog box, display the Support tab, and click Details.) To improve performance, Windows XP stores resolved addresses in the ARP cache for a short time. Some networking problems are caused by ARP cache entries that are obsolete or incomplete. The cache is normally flushed regularly, but the repair tool forces a flush. This is the same as running the following command:

       arp -d

    Tip

    To see the contents of the ARP cache, run the following command:

       arp -a

    You’ll see output similar to the following:

       Interface: 192.168.1.101 --- 0x2

    Internet Address Physical Address Type

    192.168.1.1 00-12-17-8c-48-88 dynamic

    192.168.1.100 00-11-24-1a-7a-fc dynamic

    192.168.1.103 00-11-11-be-c7-78 dynamic

  • Flushes the NetBIOS name cache—NetBIOS handles the conversion between the network names of computers and their IP addresses. To improve performance, Windows XP stores resolved names in the NetBIOS name cache. To solve problems caused by NetBIOS name cache entries that are obsolete or bad, this step clears the cache. This is the same as running the following command:

       nbtstat -r

  • Re-registers the computer with the network’s WINS server—The repair tool asks the WINS server to release the computer’s NetBIOS names that are registered with the server and then re-register them. This is useful if you’re having problems connecting to other computers using their network names. This is the same as running the following command:

       nbtstat -rr

  • Flushes the DNS cache—DNS handles the conversion of domain names to IP addresses. To improve performance, Windows XP stores resolved domain names in the DNS cache. To solve problems caused by DNS cache entries that are obsolete or bad, this step clears the cache. This is the same as running the following command:

       ipconfig /flushdns

  • Re-register the computer with the DNS server. This is useful if you’re having trouble resolving domain names or if you’re having trouble with a dynamic DNS server. This is the same as running the following command:

       ipconfig /registerdns

To launch the repair process, you have two choices:

  • In the Support tab of the connection’s Status dialog box, click Repair

  • In the Network Connections window, right-click the connection and then click Repair

The Repair Connection dialog box appears (where Connection is the name of the connection you’re repairing) and shows you the progress of the repair, as shown in Figure 4. When the repair is complete, click Close.

Figure 4. The network connection repair tool runs through six common network troubleshooting steps in an attempt to resolve the problem.


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