NetBIOS Over TCP/IP

Microsoft Windows, in its default state, uses TCP/IP, and NetBIOS Over TCP/IP, for networking. Sometimes, we forget this detail. NetBT is so easily overlooked, yet it is essential.

If we are looking at the output from "ipconfig /all", and we see

        IP Address. . . . . . . . . . . . : 192.168.1.50
        Subnet Mask . . . . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . . . . : 192.168.1.1
        DHCP Server . . . . . . . . . . . : 192.168.1.1
        DNS Servers . . . . . . . . . . . : 192.168.1.11
                                            192.168.1.33
        NetBIOS over Tcpip. . . . . . . . : Disabled
        Lease Obtained. . . . . . . . . . : Wednesday, April 16, 2003 11:19:12
        Lease Expires . . . . . . . . . . : Wednesday, April 23, 2003 11:19:12

Obviously, we're going to correct that. But what if we simply see

        IP Address. . . . . . . . . . . . : 192.168.1.50
        Subnet Mask . . . . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . . . . : 192.168.1.1
        DHCP Server . . . . . . . . . . . : 192.168.1.1
        DNS Servers . . . . . . . . . . . : 192.168.1.11
                                            192.168.1.33
        Lease Obtained. . . . . . . . . . : Wednesday, April 16, 2003 11:19:12
        Lease Expires . . . . . . . . . . : Wednesday, April 23, 2003 11:19:12

Do we see any problem there? Probably not. Look in the TCP/IP - Advanced Properties wizard, WINS tab. There are 3 possible settings for NetBIOS Over TCP/IP

• Default.
• Enable.
• Disable.

The last setting, Disable, becomes apparent when we see the first example above. But what if if we see the second example above? Well, that display can result from either the "Default", or the "Enable" setting. If it's not showing Disabled, it could be either.

The Default setting, according to the wizard, is for

Use NetBIOS setting from the DHCP server.

If your LAN

• Has a domain.
• Has computers running only Windows 2000, Windows 2002 (aka Windows XP), and Windows 2003 (aka Server 2003).
• Uses DNS, properly setup, for name resolution.

then you may wish to disable NetBT, and use directly hosted SMBs.

But what if your LAN has a NAT router providing DHCP services, and / or has no domain? NAT routers are Operating System independent, and NetBT is a Microsoft Windows Networking feature. NAT routers have no setting for NetBIOS Over TCP/IP. If you select "Default", and you have a NAT router, what network functionality do you get?

The challenge is that this one setting affects multiple functions between your computer, and other computers, in both directions.

1. Browsing: Ability to see other computers.
2. File sharing: Ability to access resources on other computers.
3. Name resolution: Ability to find out the addresses of other computers.

Depending upon what network hardware and software you have, any or all of the above functions may or may not work, in either direction (incoming or outgoing), between any pair of computers. And each different pair of computers may yield a different set of symptoms. If you have a NAT router providing DHCP services, the only way to deal with this reliably is to Enable NetBT consistently, on all computers.

In the TCP/IP - Advanced Properties - WINS wizard for all relevant network connections,

• Select the radio button "Enable NetBIOS over TCP/IP".
  
• Hit OK 3 times.
  
• Close Network Connections, after enabling NetBT on all relevant network connections.
  

If you still see

        NetBIOS over Tcpip. . . . . . . . : Disabled

after Enabling NetBT, check the TCP/IP NetBIOS Helper service.

Be safe - don't settle for "Default".

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