All MS Windows machines employ an in-memory buffer in which is stored the NetBIOS names and IP addresses for all external machines that machine has communicated with over the past 10 to 15 minutes. It is more efficient to obtain an IP address for a machine from the local cache than it is to go through all the configured name resolution mechanisms.

If a machine whose name is in the local name cache is shut down before the name is expired and flushed from the cache, then an attempt to exchange a message with that machine will be subject to timeout delays. Its name is in the cache, so a name resolution lookup will succeed, but the machine cannot respond. This can be frustrating for users but is a characteristic of the protocol.

The MS Windows utility that allows examination of the NetBIOS name cache is called “nbtstat.” The Samba equivalent is called nmblookup .