Windows 10: Case sensitive DNS error

  1.    18 May 2018 #1

    Case sensitive DNS error


    I upgraded to Windows 10 v1803 last night, and in general all worked well. However I could not remote desktop into my work laptop. I work from home, and it is easier if I dial in to my machine from my main pc (3 screens, nice desk etc.). After about an hour of trying to connect, I found that if I entered my laptop name in lowecase I could connect and remote desktop worked as it should.

    I then tested a ping. If I ping my laptop in uppercase I get "Ping request could not find host". If I change any of the letters of my laptop name to lowercase it pings correctly. I have a number of other devices in my network, which I can ping in any case, it is just this machine that is the issue.

    Now this of course is not a major issue, but I am just curious if anyone has come across this before and has any idea on what the cause may be.

    Many thanks,

      My ComputerSystem Spec

  2.    19 May 2018 #2

    I ran into this earlier this week in trying to use Remote Desktop Connection to get to one of my laptops. It's related to the RDP certificate for the remote device. While machine names are not case-sensitive, certificate names are indeed case-sensitive. Upon seeing your post just now, I said "Hmmm. I wonder if this applies to me, too?" Here's what I just produced from my own network:
    Click image for larger version. 

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    Notice that when I ping the working certificate name ("t520") the command completes successfully. But when I ping the very machine name that shows up in the ping reply ("T520") it fails. This tells me there's a problem with name resolution for machine names caused by case sensitivity. I think it's probably certificate related, but I'm not entirely sure. I'm going to report this to MS via the Feedback Hub. I'll post a link here after I do that. We should ALL upvote it. This is NOT the way that UNC names are supposed to work on MS networks!

    PS Added 10 Minutes Later: Now posted to Feedback hub as "Machine names now case-sensitive on the LAN." Please Upvote!

    PPS: Now that I think further on this, this cannot be a DNS Issue. DNS does not resolve local UNC names: that's a NetBIOS thing. See this MS Support article for an explanation Microsoft TCP/IP Host Name Resolution Order. If you read it through, it doesn't get handled until step 4 "the NetBIOS name resolution sequence." To confirm this, you can easily check that nslookup won't resolve machine names in any case (Upper/Lower/whatever). Interestingly, while nbtstat works on my LAN it is completely case-indifferent. This just keeps getting weirder!
    Last edited by EdTittel; 19 May 2018 at 10:18.
      My ComputersSystem Spec

  3.    19 May 2018 #3

    Hi Ed,

    Glad I am not the only one with this issue. I think it definitely has something to with the Windows update for me, as the day before I upgraded, I could connect to my laptop entering the name in uppercase. Are you running v1803 of Windows 10?

      My ComputerSystem Spec

  4.    19 May 2018 #4

    Yes, I absolutely am seeing this in my half-dozen 1803 installations, and I absolutely agree with you. Please look up my post to the Feedback Hub and upvote it, won't you (search for "Machine names now case-sensitive on the LAN")? Thanks!
      My ComputersSystem Spec

  5.    20 May 2018 #5

    Hi Ed, I have upvoted it and added my own comment to the feedback.
      My ComputerSystem Spec

  6.    20 May 2018 #6

    @tp5harp: thanks! Much-appreciated. Hopefully, it will lead to some corrective action.
      My ComputersSystem Spec


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