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No dns suffixes configured, no primary dns suffix.

  1. Ping a multiple-label invalid name, that's less than 15 characters: "d1.invalid"
  2. DNS query is performed and fails
  3. then nbname (udp port 137) broadcasts are done for "D1.INVALID"

NetBIOS computer names can not contain a dot, so this NetBIOS broadcasting is pointless and is a waste of time. Why is it happening? Is there any way to disable NetBIOS fallback for multiple-label names? Without disabling NetBIOS completely, I still need it for LAN single-label name resolution.

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3 Answers 3

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It's working as designed, and there isn't anything you can do about it. True, NetBIOS names can't have dots by the standard, but that doesn't mean Microsoft isn't above extending that standard. In fact, you can name WinNT domains with dots! Because of this, Microsoft has to be sure to deal with it.

You're stuck with this (nearly) pointless waste of packets. That's just how Windows works.

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  • You may be right, but this is difficult to believe, after all, DNS fallback for NetBIOS resolution can be disabled (NetBT\Parameters\EnableDns) it seems reasonable to expect NetBIOS fallback to be somehow configurable as well. How are you so sure that it's impossible?
    – Alex
    Aug 28, 2010 at 7:29
  • @Alex I say impossible, but that's not quite true. I suspect you can disable NetBIOS resolution by turning off the 'Workstation' service. This is the service that enables accessing Windows resources over the network. Turn that off and it is just possible that NetBIOS resolution fail-back will also be turned off. I am dead certain that turning off failback just for dotted names is impossible.
    – sysadmin1138 ♦
    Aug 28, 2010 at 15:16
  • As I mentioned in the question, I do not want to disable NetBIOS. When you have no dns suffixes, single-label name resolution goes through NetBIOS and only it, which is exactly what I want on a small LAN. But I do want to disable the NetBIOS fallback when DNS is used first. This appears to have been possible with winsock 1.1 (nt4). See "ExcludedProviders" (firstvpn.com/papers/ms/tcpip.pdf) But has no effect in XP, presumably because winsock and the provider model has changed.
    – Alex
    Aug 28, 2010 at 22:07
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You can disable NetBIOS name resolution by selecting the option "Disable NetBIOS over TCP/IP" on the WINS tab of the Advanced properties of the TCP/IP protocol on the network adapter.

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-1

Short computer names cannot contain dots, but host names and full computer names can. And they can be resolved without any DNS.

It is not "waste of time". For ex., my workgroup Windows XP "Full computer name: pblack.primary.dns" (short computer name + primary dns suffix on my comp) is resolved, without any DNS server or entries in any HOSTS, both by pblack and by pblack.primary.dns

DNS is external to computer resolution mechanism which may simply absent in certain cases like small workgroup or, even does not make any sense, for ex., in internal (to computer) name resolutions.

Note that short computer name is one per computer but host names can be multiple.

Unfortunately, there is no point to seek the truth because MS docs are mess on it.

---Update1:
Broadcasts are made by ip-address.

"NetBIOS broadcast" is broadcast with preliminary resolution of NetBIOS host name to ip-address. For ex. by communicating with local cache, local DNS cache/resolver, WINS server, lmhosts, DNS Server (which may have WINS forwarding), etc.

I doubt that NetBIOS resolution is used in Windows XP (I've read that it is legacy). I am inclined to believe in CIFS/SMB or SMB direct. What is NetBIOS name when MS insists that NetBIOS is used for compatibility with pre-Windows2000 OSes?
Om my Windows XP I do not have either DNS or NBT (NetBIOS over TCP/IP) or hosts/lmhosts entries which do not hinder it to resolve host name with dots.

I always thought that NetBIOS name is single-label name and broadcast is by ip (not by any symbolic name).

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3
  • NetBIOS broadcasts from XP resolve the 15 char MAX NetBIOS computer names, not the FQDN. In fact if you ping a multi-label name longer than 15 chars it will not fallback to NetBIOS broadcasts after DNS fails.
    – Alex
    Aug 28, 2010 at 8:03
  • @Alex, see Update1
    – Gennady Vanin Геннадий Ванин
    Aug 28, 2010 at 17:37
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    this response like many of your others makes zero sense.
    – Chris Thorpe
    Oct 17, 2010 at 5:36

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