NetBIOS over TCP/IP Overview

NetBIOS over TCP/IP Overview

NetBIOS over TCP/IP or NetBT is not required for computers running Windows 2000, XP, Vista, Windows Server 2003/2008. Unlike versions of Windows prior to Windows 2000, file and printer sharing with Windows 2000, Windows XP, or Windows Server 2003 can operate without the use of NetBT, unless you use NetBIOS applications on your network, such as the Computer Browser service.

Although not required for a networking environment consisting of servers and clients that are based on the Active Directory® directory service, NetBIOS over TCP/IP is still used by earlier versions of Windows, home network and NetBIOS applications that are included with current versions of Windows.

Routers do not forward broadcasts. Broadcast frames remain confined to the local subnet. Therefore, NetBIOS name resolution using broadcasts can only resolve names of NetBIOS processes running on nodes attached to the local subnet.

NetBT uses the following ports:
· NetBIOS session traffic over TCP port 139

· NetBIOS name management traffic over UDP port 137

· NetBIOS datagram traffic over UDP port 138

Note: 1. A NetBIOS name is a 16-byte name that identifies a unique or group NetBIOS application on a network.

2. NetBT provides NetBIOS session, name management, and datagram services for NetBIOS applications running on an IPv4 network. It is not designed for IPv6.

3. The Nbtstat tool is the primary tool for collecting NetBT information when troubleshooting NetBIOS name issues.

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