Turn off Multicast Name Resolution (LLMNR) to speed up Dentrix

UPDATE 4/15/2021: IMPORTANT! The latest Windows security update, KB5001330, is causing issues with Dentrix accessing the common folder on some computers. Dentrix released a notice yesterday stating that they found a workaround: turn Multicast Name Resolution (LLMNR) back on. While this might be fine for a temporary workaround, it’s a terrible long term solution because LLMNR is a known attack vector.

On Dentrix’s Facebook page, one participant indicated that another potential workaround is to set the Hosts file on each workstation to point the server to the server’s IP address. This should bypass all external name resolution, and bypass this issue altogether. We briefly tried this method (to solve a different problem) a few months ago, with terrible results, but it might be worth trying again.

The third potential workaround is to uninstall the Windows update and force your workstations to hold off on applying the update. And then, hope and pray that Dentrix will release a patch to address this problem the right way.

UPDATE 4/2019: we upgraded to G7, and everything is still speedy. This solution still holds, for us anyway.

UPDATE 4/22/2018: I had rebuilt two of our client machines (a front desk and an operatory computer), and the staff was complaining of Dentrix being extremely slow on these two. I remembered this post, followed the directions, and boom things are fast again.

P.S. Dear Dentrix Support, stop telling your clients to go upgrade all of their machines when they experience this issue. Please try this first.

ORIGINAL POST 6/20/2015:
The Dentrix G6 installation went relatively smoothly for the Belmont office of Forever Dental. After a few days, support came in and installed eCentral so we can file electronic claims. That’s when the problems started. Specific Dentrix modules (notably, Treatment Planner and Chart) were running extremely slowly. Treatment Planner would take upwards of five minutes to open a patient chart. This made no sense: it’s a small (but growing!) second practice, and there is no reason Treatment Planner should require so much time.

Our setup is relatively simple:

  • Windows 7 running G6 Server
  • 5 Windows 7 workstations running G6 Clinical or G6 Frontoffice workstation
  • All 6 machines connected to a router and obtaining IP addresses with DHCP. Nothing fancy like static IPs, hosts files, etc.
  • LogMeIn Hamachi set up on all machines, so that we can Remote Desktop into those machines

After 2.5 hours with Dentrix, they stumbled upon a solution: disable link-local multicast name resolution (LLMNR). My theory is that Hamachi adds so many subnets as the network grows, and unless you have static IP addresses mapped to names in the hosts file, LLMNR requires each request to a name to timeout before finally identifying the proper name-to-IP-address mapping.

Yes, it worked, but even as I wrote the above, it felt wrong. So if someone out there knows what is really going on, please leave a comment!

19 thoughts on “Turn off Multicast Name Resolution (LLMNR) to speed up Dentrix

  1. I’m looking at upgrading to G6 from G4 and Dentrix has informed me that I should NOT use Windows 7 Pro as my Server OS anymore. I have Windows 7 Pro on my existing Server ( Version G4 8.1) They recommend Server 2012 R2 64 bit. Any thoughts on this? I noticed that your setup shows running Windows 7 on your Server. Thanks, Greg

    • We did use Windows 7. Dentrix Support ended up requiring us to sign a waiver indicating that if it didn’t work, it’s not their fault. Something about scalability issues with Win7 as the server with lots of workstations.

      After six months in this configuration, it works just fine. We have 14 workstations on our network. We don’t have to deal with the complexity of Windows Server. And it gives us options to use things like Acronis Backup ($100 for Win 7 vs. $1000 for Win Server 2012!). But, certainty, there was much gnashing of teeth when we decided to go this route initially.

  2. Thank you for figuring this out. Dentrix did the same thing to one of our clients by making them sign a waiver and then saying they needed a new server. Your fix did the trick. Chart and Treatment Planner were very slow to open and many times would just crash after the office had Dentrix upgrade them from G4 to G6.1. They worked for hours with a tech and the conclusion was that Windows 7 was not a supported server OS and that they needed to upgrade. I applied your fix and it worked immediately.

  3. Can you confirm that Dentrix requires all the client machines need to be run with administrative privileges? That seems crazy from a security perspective.

  4. Troubleshooting a local g5 install 2ith network problems. Everything in dentrix seems to work however the patient chart module will not open at all. Does the server for G5 actually require a static IP address? The weird thing that I’ve noticed with this G5 install is that the majority of the time many of the workstations cannot see the server under Network comma however if you put in two backslashes and the host name it will come up and display its shares. I’m very confused however I think this has something to do with the problem. Any suggestions would be greatly appreciated.

    • I don’t think the G5 server requires a static IP address, as it uses NetBIOS (a Windows feature) to map server names to IP addresses. Personally, this sounds like a problem with your router or hub, or with your Windows configuration. You probably need to contact Dentrix Support for this one.

  5. I stumbled upon this website while I was investigating LLMNR during a network trace of my home network. I was curious to see how Windows 10 Home Edition was resolving my networked printer NETBIOS name. To my surprise, LLMNR was providing the resolution. My epiphany came when I saw the source was an IPv6 address. I generally turn off IPv6 on my home network. I configured TomatoUSB on my router to handle WINS resolution and I need to learn more about LLMNR. Hope my finding helps you somehow with your issue.

  6. Has anyone had issues with modules loading slowly in D6 even taking out the name resolution issue? We have a Windows Server 2012 that is even loading the modules slowly (30 Seconds to load patient chart). Server is under-utilized.

    • Yes, several times for us. Unfortunately, I was not around when Dentrix Support logged in and “did something” to fix it. In one instance they even uploaded and ran a binary tool called “fix slowness” or something similar! Not good.

  7. Did any one try G6.1 server install on Windows 10? Dentrix support said that it is not supported operating system. I moved one of my workstations to windows 10 and it seems fine. The server is running on Windows 7 Pro.


  8. drdonbell@hotmail.com
    I am having problems with my G4 Dentrix appointment book system at the front desk work station and also with my Kodak digital radiographic system working very slow or not responding at all. Will disabling the LLMNR help? Any ideas?
    Dr. Don Bell

  9. has anyone had any issues with the Reporting in Dentrix G5.2? When I run a report (print preview or print), the report just hangs or actions like it’s processing. I’ve been waiting over 20 minutes now.

  10. Noticed the same Multicast problem which caused Chart and Ledge to open very slow (up to 10 times slower). You post gave me more insight about the problem.

    Also Windows Workstation 7 Pro is just fine for support over a dozen client computers. Using Windows Server 2012 (or any other version) will create other problems such as some favored apps will not able to run at all, besides extra management work.

    10 years ago, we can use a lot slower Windows XP computer as a Dentrix server to support a dozen computers and didn’t feel much speed problem, so any performance problems with today’s lot fast hardware is indeed not a hardware issue but a software issue. So telling people to use Windows Server in order to solve speed problems was a marketing strategy that Microsoft want you believe. Dentrix support was doing just what Microsoft (and hardware vendors) wanted them to do, I dare to say.

    Thank you for your post so we can solve a big problem properly.

  11. Jason, what a great post for people to find. We are in a dilemma as we are using G4 and would like to upgrade dentrix but were given a scare with their server requirements. We are at a point that G4 seems to be slowing our office down now as far as features. Trying to build a new server with Windows Server 2016 is such a huge financial bill (not to mention the IT cost and training). All our computers are running Windows 7 Pro without issue.

    Can we upgrade to the latest G6 without issue still keeping windows 7 pro as the server? You have good experience with this?

    Any experience upgrading to G7? I understand this uses a completely different database however.

    I know this post is more than a couple years old but thanks for your helpful post!

    • Jerome,
      Thanks for your comment. I only have experience upgrading to G7 once, and it was a few years ago. It went relatively smoothly (except for this specific issue), and we are still running Windows 7 Pro today. I know that if you have Dentrix try to assist you with this upgrade, they will require you to sign off on a statement indicating you understand that the requirements state Windows Server and that they cannot help you if things go wrong (or something to that effect). That is why I went through documenting all of this into this (and related) blog posts.
      Good luck!

  12. Pingback: How we speed up Dentrix clients on our network | Jason Shah

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