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Troubleshooting techniques

How can I change my media access control (MAC) address under Windows NT 4.0?

Each network adapter card has a MAC address, which workstations on local subnets use to talk to each other. MAC addresses are usually burned into the adapters during the manufacturing process. To overwrite a network adapter card's default MAC address, perform the following steps:

  • Start the registry editor (use regedit.exe)
  • Navigate to KEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\<networkadapter>\Parameters
  • From the Edit menu, select New-String Value
  • Type a name of Network Address, and press Enter
  • Double-click the new value, and enter the adapter's new MAC value
  • Click OK
  • Close the registry editor
  • Reboot the machine

How do I create a password reset disk for a computer that's a member of Windows XP domain?
You can't create a password reset disk for a domain account, but you can create this disk for a local account on a machine that's a member of a domain. To create the disk, perform the following steps:

  • Press Ctrl + Alt + Delete to open the Security dialog box
  • Click Change Password
  • Select Log on to specify the local computer
  • Click Backup to start the Forgotten Password Wizard
  • In the "Current user account password" box, type your password and click Next
  • The Forgotten Password Wizard creates the password-reset disk. Click Next, then click Finish. The Forgotten Password Wizard returns you to the Change Password dialog box.
  • Remove the password-reset disk. Label the disk and store it in a safe place
  • Click Cancel to exit the Change Password dialog box
  • Click Cancel to exit the Windows Security dialog box

Is it possible to join a broken CAT5 cable by soldering the parts back together?
Soldering may cause problems, as CAT 5 cable insulation melts extremely fast even with low wattage irons. The wires cannot be untwisted more than ½ inch total. Use shrink-wrap if you try soldering. Crimp an RJ-45 plug on each end of the broken cable and "glue" them back together with a CAT 5 coupler. Be sure the coupler and plugs are rated for CAT 5 or 5e and that the plugs match the type of cable. There are plugs for stranded core and solid core cables. Horizontal runs are supposed to be solid core and can be up to 90 meters long (100 meters if connected directly from a hub or switch to a PC). The coupler may effectively reduce this length somewhat.

What is Pathping?
Pathping, a utility that's new to Windows 2000, is something of a cross between the Ping and Traceroute utilities. The Pathping utility sends packets to each router on the way to a final destination over a period of time and computes results based on the packets that return from each hop. Because Pathping shows the degree of packet loss at any given router or link, you can determine which routers or links might be causing network problems.

I would like to know how to check or see which TCP ports are in use?
The Netstat command can list currently used ports, which might be helpful if you suspect an application is clashing with another one on an active port. Use the -an switch to show all connections and listening ports in numeric form.

C:\> netstat -an

Check the output for any port that you think your program might use.

Can I run voice and data (Ethernet) through the same cable?
The same cable can be used for running voice as well as data applications though it is not recommended. If you use the same cable for both voice as well as data, this will open your network to interference and other performance issues (when your phone rings the line is carrying a 90V AC signal). This may limit the future flexibility of your network. You also run the slight risk that a 40-100VDC-telephone signal might get inadvertently connected to your network card. It is best to think of each cable that is to be used for networks as a single purpose device. Your network will not be Cat5 compliant if you do this.

What is a 'stackable' hub, why would I want one?
Stackable means that two or more hubs can be connected via a special cable so that the number of ports is increased, without adding more 'hops' to the network. The typical way to add another hub to a network is by using a regular Ethernet crossover cable to go between one port on each hub. This creates a 'hop', which can cause more delay in the network. For two hubs, this hop will hardly be noticed, with many hubs, the additional hops may violate Ethernet specs. Typically you want 4 (or less) hops between any two nodes on the network.

I'm setting up a local area network and want to use TCP/IP and private IP addresses. What IP addresses should I use?
The Internet Assigned Numbers Authority has reserved the following ranges of IP addresses for use in private networks: - - -
Examples of private network addresses are:,,, ..., subnet mask,,, ..., subnet mask

I want to copy files from one computer to another, but there are too many files to do it with a floppy disks. Is it possible to connect them using a cable?
There are many ways to connect two computers running Windows:

1. Use the DOS programs Interlnk and Intersvr to make a serial or parallel port connection. File transfer is possible only from the Intersvr machine to the Interlnk machine.

2. Use Direct Cable Connection to make a serial or parallel port connection. File transfer is possible only from the "host" machine to the "guest" machine.

3. Create a peer-to-peer Ethernet network. You install an Ethernet adapter on each machine and connect them with networking cables. Most Ethernet adapters plug into PCI or ISA slots inside the machines. If you don't want to open the machines, use Ethernet adapters which connect to USB ports.

Ethernet connection has two distinct advantages: it is the fastest and it provides two-way connectivity. Additionally, each machine can access files and printers on the other.

I use the IPX/SPX protocol for multiplayer games. I would also like to use it for file and printer sharing. I tried doing that but can't get all the computers to see each other.

Problems with IPX/SPX can usually be resolved by tweaking some settings in the IPX/SPX- NIC properties on all of the networked computers:

NetBIOS tab: enable NetBIOS support.

Advanced tab: specify an explicit frame type, such as Ethernet 802.3.

Advanced tab: set all of the Network Addresses to the same value.

Why is that we cannot join a Windows NT 4.0 domain to a Windows XP or Windows 2000 client?
Windows XP and 2000 use DNS instead of NetBIOS to name domains. As a result, if you've installed only TCP/IP on the XP or Win2K client and you've disabled NetBIOS over TCP/IP, the client can't join an NT 4.0 domain. To enable NetBIOS over TCP/IP, perform the following steps:

  • From the Start menu, select Settings, and click Network and Dial-up Connection
  • Right-click Local Area Connection, and select Properties from the context menu
  • Click Internet Protocol (TCP/IP), and click Properties
  • Click Advanced, and select the WINS tab
  • Click "Enable NetBIOS over TCP/IP"
  • Click OK, and ignore the WINS error
  • Click OK to close all dialog boxes.

If you don't want to use NetBIOS over TCP/IP, you can instead use NetBEUI on all clients.

How can I tell if a Dynamic Host Configuration Protocol (DHCP) Server is running/working on my network?

DHCP allows you to establish a range of valid IP addresses to be used per subnetwork [,,…, comprise a subnetwork].

An individual IP address from the range is assigned dynamically to any DHCP client requesting an address. DHCP also allows you to establish a lease time that defines how long an IP address is to remain valid. Other configuration parameters can also be assigned using DHCP, such as subnet mask, DNS and WINS server identification, and so on.

Windows 9X/Me: Click Start, Run, enter winipcfg, click the More Info button, select the appropriate network adapter, and see if there is anything in the DHCP Server box. Click release followed by renew to test the DHCP server.

Windows 2000 and NT (and probably Windows XP): Start, Run, enter cmd, and type the following in the resulting DOS window:

C:>ipconfig /all
C:>ipconfig /?
Ipconfig also works with Windows 9X/Me.

How do I test an Ethernet network interface card (NIC)?
Most NICs or network adapters come with one or more floppy disks containing drivers, etc. for various operating systems. These floppies also usually include a diagnostic program to test the NIC. Many of these programs are DOS-based and must be run by booting the computer to DOS or from a DOS window. Unless you have a loop back plug installed, the loop back test will probably fail. A loop back plug directs signals from the NIC's transmitter back to its receiver. An indicator that NIC and cabling is functioning is to check the LINK (sometimes labeled LNK) and Activity (ACT) LEDs, if there are any, on the NIC and on the device at the other end of the cable. The LINK should be solid with no flickering and the ACTIVITY should be blinking, which indicates network activity. This indication is not as thorough a test as the diagnostics program and it is not foolproof.

The diagnostics program and LED observations may not conclusively show that the NIC is fully functional in Windows. Look for exclamation marks beside the NIC driver in the Windows 9x/Me Device Manager (click Start-Settings-Control Panel-System-Device Manager...), which indicate a resource conflict and run the Windows Resource Conflict Troubleshooter if you find any.

Look for multiple instances of the NIC driver in the network configuration (click Start-Settings- Control Panel-Network and remove all of them, if you find any. Restart Windows and reinstall the driver. Run hwinfo (click Start-Run and type hwinfo /ui). To help narrow-down problems, click View in the main menu and select Devices with Problems. Once these steps are completed and the NIC passes, try copying about 100 Mb of files to another computer on the network. Net diag and ping are useful tools for further testing a NIC and a network. For more info, open a DOS windows and type:

C:\>ping /?
C:\>net /?

Ping requires that the TCP/IP protocol be installed, and IP addresses be assigned at both ends of the network segment to be tested.

Net diag is a useful low-level network test.

How can I get Network Neighborhood to appear on the desktop?

Run Tweak UI, go to the Desktop tab, put a check mark in the Network Neighborhood box, and click Apply and OK. If this doesn't work, go to Control Panel-Network. Remove Client for Microsoft Networks if it is present. Then add Client for Microsoft Networks. There might be a system policy hiding Network Neighborhood. Run the registry editor, open this key:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer and delete the value named "NoNetHood".

I have a connectivity problem to my ISP. Windows 98 takes forever to connect to the ISP. It says "Logging on to network..." and just sits there. What's happening?

Go to My Computer-Dial-Up Networking. Right click Your connection and select properties. Under the Server Types tab, un-check the Log on to network box.

On Windows 2000/ME (client machine), I am unable to connect to my RAS server using dialup. It gives error 619, port was disconnected. But I am able to connect to the Internet thereby ruling out problem of modem connectivity. I am able to connect to RAS server on Windows 95/98 but not on Windows 2000/ME (client machine). Kindly help.

This issue occurs because the account you were logged on with at the time you joined the domain did not have administrator privileges on the Windows 2000 domain. Because of this, services that could easily compromise network security, such as RRAS, deny clients the ability to obtain access to the domain.

I would suggest that you do the following to solve the problem:

Firstly you must register the RRAS server in Active Directory using an account that has domain administrator permissions. To do so follow the steps below:

  • Add the RRAS Computer to the appropriate group: Log on your Windows 2000-based computer with an account that has administrator privileges for Windows 2000 domain.

Note: This method may be used with Windows NT/2000-based RRAS or RAS servers.

  • Launch the Active Directory Users and Computers MMC snap-in and then double-click your domain name.
  • Double-click the Users folder, and then double-click the RAS and IAS Servers security group.
  • Select the Members tab.
  • Add the RRAS server to this group.
  • Use the Netsh.exe Utility

Note: The Netsh.exe methods can only be used if the RRAS server is Windows 2000-based.

Use either of the following methods with the Netsh.exe tool:

Method 1: Log on the RRAS computer using an account that has domain administrator privileges, type Netsh. RAS add registered server at a command prompt, and then press enter.

Method 2: To run a command with administrator privileges without being logged in as an administrator:

At a command prompt on the RRAS computer, type run as /user:domain name\administrator name "cmd", where domain name is the appropriate domain name, and administrator name is the appropriate administrator name. You are then prompted to enter a password for this account. If this computer is able to connect to the domain controller and verify the credentials, a command prompt opens with the following information in the title bar: cmd (running as domain name\administrator name)

At a command prompt, type Netsh. RAS add registered server at a command prompt, and then press enter.

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