Sams Teach Yourself Network Troubleshooting in 24 Hours:Hour 11 Windows Networking Basics

NetBIOS

NetBIOS (Network Basic Input/Output System) provides name services and session services to the file- and print-sharing programs between two computers. Windows can use the nonroutable NetBEUI protocol to transport NetBIOS to another computer; alternatively, TCP/IP or IPX/SPX can be used in a routed environment.

Specifically, NetBIOS handles name services for Microsoft (and older IBM) file and print services. It also serves to carry messages pertaining to the creation of workgroups on the network and makes sure that no duplicate workstation names exist within the workgroup or domain.

One type of NetBIOS error is very common. It occurs when a technician duplicates a “known good” hard drive (see Hour 15, “Beauty Is Consistency Deep”) to a “known bad” hard drive and then reboots the problem station. Immediately, he or she sees the following Windows error, which is in fact a NetBIOS error:

Microsoft Networking:

The following error occurred while loading protocol number 0.

Error 38: The computer name you specified is already in use on the
network. To specify a different name, double-click the Network icon in
Control Panel.

NetBIOS has queried the network to see if the name exists, and, in fact, it does. Of course, the tech simply goes to the Control Panel, clicks the Identification tab, and changes the PC name to fix this problem. This also happens when two people name their workstations the same (like if you had two 2001 fans name their PCs “HAL”). Because it doesn’t really matter what a PC is named, if you see this error, you can simply pick a different but similar name, such as “HAL2000.”

Browsing

Can the protocol itself deal with the creation of workgroups? No, this task requires a service program on the other side of the wire. You should know that a mechanism, called browsing, exists that’s part of workgroup or domain network computing.

The browse system consists of a browse master, backup browsers, and client computers. Any client computer can get information about network resources, whether the resources are servers, workgroups, NT domains, and so on. For example, when you click your Network Neighborhood icon, the computer list you see is obtained from the browse master of your workgroup or domain. As you can see, browsing is pretty important—if you can’t see the resource, you can’t use the resource.

A Windows 95 computer will only show up on the browse list if it’s acting as a server. To make your Windows 95 computer act like a server, do the following:

1.  Open the Windows Control Panel by clicking Start|Settings|Control Panel.
2.  Click the Network icon.
3.  Click Add.
4.  Select Service.
5.  Click Microsoft and then select File and Printer Sharing for Microsoft Networks.
6.  Insert the Windows CD-ROM if prompted and reboot when asked to do so.

I once saw a case in which a user absolutely could not browse others in her workgroup. After checking the network card and cable and finding nothing wrong, we were on the verge of reinstalling Windows—we had tracked the problem down to something about the OS. Before doing this, we checked the Control Panel again; this time, we noticed that the workgroup name had a space in front of it. Argh! We removed the space, and suddenly we could see everybody else.
I’ve also seen a case in which a workgroup, B&O, was mistyped as B&0 (with a zero rather than the letter O). Be sure to watch out for mistyped workgroup names.

The browse master of an NT domain will always be the NT server that’s the primary domain controller (PDC).

Although an NT domain can exist across subnets (that is, via a router), workgroups cannot. Instead, the workgroup exists twice on the two different segments, each one with its own browse master and browse list. That means the browse master on network A has no idea what the browse list is for network B. Computers on segment A will not be able to see those on segment B in their network neighborhood, and vice versa.

The browse master of a workgroup or domain is the machine that’s responsible for keeping a list of participating workstations. If the browse master leaves the workgroup, another browser from the backup browser list must take over. This is only important because mentally ill browse masters have been known to spring up on Windows networks, and this can cause problems. Also, if a workstation claims that it’s the browse master when it’s not, this can also cause problems.

SMB

Once names are established and workgroups are joined, Windows file- and print-sharing happens through a mechanism called server message block, or SMB. SMB is featured in NT and Windows 9x, but the versions are different. The SMB server program is what makes it possible for other PCs to share a server’s files and printers. Contrariwise, the SMB client program on a client PC makes it possible to use SMB-offered files and printers on a server. SMB and NetBIOS are somewhat joined at the hip—for example, SMB gets its name resolution from NetBIOS. You cannot run SMB without NetBIOS somewhere in the picture.

In fact, Microsoft networking’s multilingual capabilities are predicated on the fact that TCP/IP and IPX/SPX have a facility to carry NetBIOS. If you turn this off in the Control Panel, say goodbye to Microsoft file and print (unless you have NetBEUI installed).

SMB is pretty simple stuff, and it rarely breaks. Problems with SMB usually tend to lie in protocol problems, name service .problems, WINS problems, DHCP problems, and domain and/or security problems.

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