Disappearing DNS Servers

I had prepared a draft blog about Version 6.0.6278.27 of the DNS MP (14/8/2008). It is very noisy but having installed it in a couple of environments and read through the MP guide I think I had a handle on how to tune it. But rather than publish that I am posting this instead.

I am about to remove that MP from the environments that I have installed it in and replace it with the old version. The reason being is that the DNS servers seem to disappear from the discovered DNS servers list and sometimes come back but generally not. I picked up this from the newsgroup and initially I did not see that problem but then it happened to me and a few other people have replied that it has happened to them as well. So it does not matter how much better the new MP is (or not depending on how you view noisy MPs) but if it is not running the rules on the servers it is supposed to then there is no point in deploying it.

I did turn on the trace and watched the events come in and looked at the script to see how the script was working. And for non DNS servers the discovery failed and exited which is fine. For DNS servers they all exited OK but only some of them had the event to say they were putting in discovery data and that matched the list showing in the console. There appears to be no rhyme or reason why some DNS servers put the data in and some do not and looking at the script it is not obvious why this is happening. There was a report that upgrading to .Net 3.5 sorted it out but I had some servers on that version that were in the discovered list and some that were not. So far no response from Microsoft on this but it is difficult to recreate as my servers were all discovered for a few weeks before some of them disappeared. Very strange. If you are running this MP it is worth checking that it has found all your DNS servers.



  1. John W.

    Thanks for posting this Ian. We have experienced this as well and we are planning on rolling back to the previous DNS MP as well.


  2. Hello Ian, not sure if you remember me or not, but I susbscribe to your post and was concerned about this issue. I raised it with our DNS MP program manager and she would like some more information from you if that’s possible. Can you shoot me an email please? Thanks, Justin

  3. Hi Ian,

    First thanks to add my blog in your list 🙂

    My environment is mixed SCOM / MOM as we are in a transition. I noticed about those DNS discovers that SCOM’s discovery works fine (send discovery data) just once after the MOM DNS discovery. Then next discoveries go wrong again and servers disappear. Really strange behaviour. We may also return to the previous version of the MP.


  4. Daniele

    Hi Ian,
    the discovery script has a bug when the WMI query fails, in this case it will return an empty discovery document, this in turn will delete the previous discovery. This explains the flip flop behavior with disappearing and reappearing DNS Servers. It must be added that the discovery runs every 15 mins making this more visible. I developed a quick fix that disables the out of the box discovery and enables a new one with a more error proof script. Drop me a mail if you’re interested.



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