Q. What are the NetBIOS-over-TCP/IP name-resolution types?

A. Windows resolves a NetBIOS name to an IP address in three ways:

  • a lookup in the LMHOSTS file
  • a broadcast on the local subnet
  • a request to a WINS server

Windows resolves NetBIOS names by using one of the following four methods. (The value in parentheses is the WINS/NetBT node type setting, option 46, which you must specify when you configure TCP/IP on a Windows network.) Those four methods are:

  • B node (broadcast, 0x1)--Windows uses broadcasts for both name registration and name resolution. Depending on gateway configuration, a B-node client might not be able to send packets beyond the local subnet. Therefore, B node isn't suitable for large networks. Microsoft actually modified the standard B-node type so that Windows tries to resolve the name first by checking the LMHOSTS name cache. If that doesn't work, Windows sends a broadcast. Then, if the broadcast fails, Windows tries to resolve the name by checking the actual LMHOSTS file.
  • P node (point-to-point, 0x2)--This method doesn't use a broadcast. Instead, at start-up, the computers on the network register their names with the configured WINS server that's also on the network. When a computer needs to resolve a name, it sends the resolution request to the WINS server. This method works as long as the WINS server is up and running. If the WINS server fails, resolution can't occur.
  • M node (mixed, 0x4)--Windows uses B node (i.e., broadcasting) first and, if it fails to resolve the name, uses P node (i.e., it checks the WINS server). M node isn't the best solution because it uses broadcasts initially, which takes longer and uses more network resources than issuing a request to the WINS server.
  • H node (hybrid, 0x8)--Windows uses P node first and, if it fails to resolve the name, uses B node. Therefore, Windows uses a broadcast only when the WINS lookup fails (which isn't likely). Typically, H node is the best method to use and is the default.
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