NetBIOS
In a Nutshell - CIW Course Section 3, Part B1, Chapter 5
NetBIOS Features
NetBIOS or the Network Basic Input/Output system is an alternative name resolution system to DNS. NetBEUI is a protocol developed by Microsoft for NetBIOS, it is a non-routable protocol which means it can only be used on a LAN. NetBIOS will run on a TCP/IP network.
NBTSTAT Command
The nbtstat command displays protocol statistics and TCP/IP connections on networks running NetBIOS over TCP/IP. This is available from the command line and has a number of Windows 2000 options.
NBTSTAT Options
NetBIOS Ports
- 137 - supports the NetBIOS naming service
- 138 - carries the NetBIOS datagram service
- 139 - carries the NetBIOS session-layer protocol
NetBIOS Names in Windows: Resolving
Windows 2000 supports four methods of resolving a NetBIOS name to an IP address. They depend on the node type configured for the node. They are broadcast (B-node), peer-to-peer (P-node), hybrid node (H-node) and mixed node (M-node). The NetBIOS Name Resolution Process uses a number of methods to try and resolve a name to an address. These steps and the order in which they are attempted are shown below:
- NetBIOS name cache is searched
- WINS server is queried
- B-node broadcast is generated
- LMHOSTS file is consulted
- HOSTS file is consulted
- DNS server is queried
A B-node broadcast is a bandwidth hungry method of name resolution and is limited to a single subnet of the local network as this traffic cannot cross a router.
P-node only uses a NetBIOS Name server (NBNS) such as WINS server to resolve NetBIOS names. P-node does not use broadcasts, so if the name server is unavailable, name resolution cannot take place.
The LMHOSTS and HOSTS files are text files containing node names and IP addresses. These files are, generally, located in the systemroot\system32 folder.
NetBEUI is seldom used these days, the course claims that Windows 2000 and XP support it by default, which it may. I looked on my XP machine, it is not installed and is not available as an additional protocol to be selected.