Windows Enterprise Desktop

May 23 2018   1:15PM GMT

Win10 NetBIOS Names Get Weirder

Ed Tittel Ed Tittel Profile: Ed Tittel

Name resolution
Windows 10

Last Friday, I observed in a post here that machine names appeared case sensitive in RDP. Indeed they are — kind of — and in other places, too. This includes the ancient and venerable PING command, a go-to utility to check connectivity between IP hosts. In trying to get all of my PCs to show up on the LAN, I turned to PING to see who was reporting in and who wasn’t. Along the way I observed some fascinating and surprising case sensitivity in PING itself. Here’s an illustrative screen capture from PowerShell:

Win10 NetBIOS Names Get Weirder.dvp-ping

An abridged version of PING attempts using the same base string, with differing upper- and lower-case chars.

Why I Insist That NetBIOS Names Get Weirder and Weirder

The following table sums up the results from the preceding sequence of PING attempts (plus another item I chose not to include). It basically shows that NetBIOS name resolution has its apparent quirks.

Variations on a NetBIOS name: DellVP11
Name string Ping result Capitalization map
dellvp11 succeeds llllllnn
Dellvp11 succeeds Clllllnn
DEllvp11 succeeds CCllllnn
DELlvp11 succeeds CCClllnn
DELLvp11 succeeds CCCCllnn
DELLVp11 succeeds CCCCClnn
DELLVP11 succeeds CCCCCCnn
DellVP11 FAILS ClllCCnn
DellVp11 succeeds ClllClnn (not shown)

To me, there’s one captivating thing about the outputs. The only string that DOESN’T work is also the same string that PING uses itself — namely, DellVP11. That’s ClllCCnn, in the notation of the table. This denotes: initial cap, followed by three lower-case letters, two more cap letters, and two digits, in case you wondered.

A Surprising Finding for NetBIOS Names

It turns out there’s good reason for PING to use that specific NetBIOS name for the Venue Pro. The Microsoft Developer Network Documentation says this about NetBIOS names (emphasis mine):

Neither [RFC1001] nor [RFC1002] discusses whether names are case-sensitive. This document clarifies this ambiguity by specifying that because the name space is defined as sixteen 8-bit binary bytes, a comparison MUST be done for equality against the entire 16 bytes. As a result, NetBIOS names are inherently case-sensitive.

There’s only one way I can find to get the “real NetBIOS name” for a Windows 10 computer. It requires checking the Computer Name field in the Control Panel’s System element. On my Venue Pro, that field reads “DellVP11” (ClllCCnn). Go figure! It’s the only name that DOESN’T resolve in PING. This makes no sense to me whatsoever, but it’s indisputably true — on this particular PC at least.

On some of my other PCs, PING accepts all variants of the machine name. The case of individual letters doesn’t matter. On others, it does. As I’ve already reported for my T520 Lenovo laptop, “T520” doesn’t work but “t520” does– and the latter is the apparent actual NetBIOS name string. For my X220 Tablet, “X220T” doesn’t work, but all three other possible variants do (“x220T” “X220t” and “x220t”, of which “x220t” is the actual NetBIOS name string).

Again: weird! I sure hope MS comes up with some kind of fix for this. Because most IP utilities report the machine name in upper case only, seems like that should be the canonical form for such names. We’ll just have to wait and see how it all plays out…

4  Comments on this Post

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  • runeterkel
    Hi Ed

    I have also observed the problem, this with an MFP device.
    I don't know if you can use some of my information, but my problem is similar, you can see if you can disable Ipv6 this might help.

    I don't know if it is the way that some Triumph-Adler (Kyocera, Copy Star)models are responding to the ping of the hostname when Ipv6 is enabled in the interface of the MFP. 
    But when I disable IPv6 I can ping the hostname in Capital Letters. 

    It is not all machines that the problem exist on 
    Problem with  TA P-C2155w MFP updated with the newest firmware in KFS/TA Fleet 
    Problem with TA P-C3560i MFP updated with the newest firmware in KFS/TA Fleet 
    Problem with TA 350ci  System firmware : 2R6_2000.004.113 Engine firmware: 2R6_1000.003.004 Panel firmware: 2R6_7000.004.101     Problem reported by the dealer on this machine 
    OK DCC2930/3050ci with Ipv6 enabled

    When you choose to install the printer with setup tool and choose to print to hostname, the port is created in Capital letters, if you manually create a new port with the hostname in lowercase the print job is released immediately. 
    But as far as I know, Ipv6 is enabled by default as the factory setting, so end customers with Windows 10 1803 update will not be able to auto-install if they choose to print to hostname, only if they disable Ipv6 on MFP, or change port name to lower case letters.  
    20 pointsBadges:
  • runeterkel
    Hi Ed

    My post was too long or I have too many pictures in it, but I think that I got posted the sentence of my post.
    Best regards
    Triumph-Adler Support Denmark
    20 pointsBadges:
  • Ed Tittel
    Your image did not come through. I do believe you did break length restrictions in the TechTarget WordPresss environment. Interesting that IPv6 gets in the way of expected behavior. I hope you post this information to Microsoft's Feedback Hub. They need to know this is going on. Thanks for sharing, --Ed--
    13,120 pointsBadges:
  • xuopark
    Thanks for IPv6 information.
    I had been suffering from the same issue, and I also got upper/lower character issue resolved after disabling IPv6.
    Fortunately, my router nor ISP doesn't support IPv6 yet.
    0 pointsBadges:

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