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Windows 2012 Server DNS issues RRS feed

  • Question

  • Hello experts,

    In our organisation, we have a Hyper-V physical server running the following virtual servers:

    192.168.0.109 Exchange 2013

    192.168.0.110 DC1

    192.168.0.111 DC2

    Default gateway for all servers and computers is a DrayTek router 192.168.0.100 

    We have a single domain in the entire organisation.

    We are facing two problems:

    1. On some computers, when we try ping mail.ourcompany.com, it resolves our public IP 185.x.x.x, while this computer is using 192.168.0.110 and 192.168.0.111 as it's DNS servers and it should resolve 192.168.0.109 instead as it's setup as an A record in our only forward zone. In other words, DNS is forwarding some requests coming from some computers to the external DNS server while it should not do forward.

    2. On computers which are using our two DNS servers, surfing the internet gets very slow and most of websites fail to open. If we change first DNS setting on any computer to 8.8.8.8 then things become well and sites open successfully. 

    Any help about solving this is appreciated. 

    Saturday, March 26, 2016 6:32 AM

Answers

  • Hi Haythamk,

    Thanks for posting here.

    >>1. On some computers, when we try ping mail.ourcompany.com, it resolves our public IP 185.x.x.x, while this computer is using 192.168.0.110 and 192.168.0.111 as it's DNS servers and it should resolve 192.168.0.109 instead as it's setup as an A record in our only forward zone. In other words, DNS is forwarding some requests coming from some computers to the external DNS server while it should not do forward.

    You could try to use theipconfig /flushdns command on your clients to flush the dns caches then try again.

    Meanwhile, you could also use thednscmd /clear:cache command on your DNS server to flush the dns caches then try again.

    >>2. On computers which are using our two DNS servers, surfing the internet gets very slow and most of websites fail to open. If we change first DNS setting on any computer to 8.8.8.8 then things become well and sites open successfully. 

    As mentioned above, if you use the public dns:8.8.8.8 as the primary dns server on your dns clients, surfing the internet very quickly and things worked well, i suppose the major issue is on your dns server's settings.

    You could try to enabled the dns log to monitor the dns service.

    Besides, please ensure that your dns servers have configured the correct forwarders and root hints.

    Please help me to check your router settings to see if there are any specific settings block or limit the access speed,e.g. firewall and etc.

    In addition, you could use the Wireshark tool to monitor the whole process during the DNS request and resolves.

    Download link:

    https://www.microsoft.com/en-us/download/details.aspx?id=4865

    Note: please also help me to check the hyper-v network settings: public/private or something else.

    Best regards,


    Andy_Pan



    Sunday, March 27, 2016 3:00 AM