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DNS Forwarder RRS feed

  • Question

  • I'm not sure i've seen this issue before. I have noticed after making a DNS change for an external DNS domain that it isn't updating when I do an nslookup with our DNS servers. 

    If i do an nslookup of the forwarder setup for the DNS servers then it resolves to the updated address. However, if i check the local DNS server it still is the old one. The only way I can force it so far to update is to restart the DNS service. I noticed one of the DNS servers is working and i don't need to restart it for it to see the changes. 

    Any idea what might be happening here? 

    Thursday, May 19, 2016 9:36 PM

Answers

All replies

  • Hi philjfry,

    >>If i do an nslookup of the forwarder setup for the DNS servers then it resolves to the updated address. However, if i check the local DNS server it still is the old one. The only way I can force it so far to update is to restart the DNS service. I noticed one of the DNS servers is working and i don't need to restart it for it to see the changes. 

    Please start from the DNS debug logging file,or event viewer,is there some associated error or event.And what os are you using?If you are using windows server 2008 or 2008r2,please check these kb:

    Windows Server 2008 and Windows Server 2008 R2 DNS Servers may fail to resolve queries for some top-level domains

    https://support.microsoft.com/en-us/kb/968372

    DNS Server service does not resolve some external DNS names after it works for a while in Windows Server 2008 R2

    https://support.microsoft.com/en-us/kb/2508835

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    Cartman
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    Friday, May 20, 2016 2:32 AM
  • The DNS servers are running Server 2012. The DNS will resolve after restarting the service but i'm not sure why that fixes the problem. The one DNS server that seems to work without restarting is also running Server 2012. Basically, the problem is I made a change to an external DNS domain and while it was still resolving, it wasn't seeing the updated DNS entry. Restarting the DNS service seemed to force it to get the new updated entry. How does forwarding work? If the forwarder has the updated entry should the local DNS server get that address as soon as the forwarder knows about the change? 
    Saturday, May 21, 2016 5:27 PM
  • It should be the caching. You can force it to be cleared by running dnscmd /clearcache. Otherwise, you need to check your record TTL - If you would like the refresh to be quicker than the TTL period should be shorter.

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    Sunday, May 22, 2016 5:28 PM
  • Mr X is correct. A DNS server will answer from cache first, then consult a forwarder second if the answer isn't found in the cache.
    Thursday, May 26, 2016 7:54 AM
    Owner