Internal DNS

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IT_Field_Support
IT_Field_Support Posts: 97  Ally Member
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edited April 2021 in Security
Hi, 

I have a quick question about usg40w router, fw 4.33. I setup a dns entry for the router, as : 
router.fqdn : xx.xx.x.xx

Ma computer has the router's IP as only DNS server.
When I test the IP resolution of the router, sometimes I got router.fqdn and sometimes myrouter.fqdn

I couldn't find any occurence of the name myrouter in my config. This is a bit confusing, where does that name come from and why it resolv randomly router/myrouter? 

Thanks,
Davy

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  • Zyxel_Stanley
    Zyxel_Stanley Posts: 1,366  Zyxel Employee
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    Hi @IT_Field_Support  

    Can share screenshot of your USG DNS setting and PC resolution result?

  • IT_Field_Support
    IT_Field_Support Posts: 97  Ally Member
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    Hi,

    For sur, here is the screenshots as asked.
     

  • Zyxel_Stanley
    Zyxel_Stanley Posts: 1,366  Zyxel Employee
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    edited June 2019
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    Hi @IT_Field_Support  

    The DNS cache on your PC is belonging to A record.

    So it means your PC has sent DNS request(myrouter.XXXX.XXX)to USG DNS.

     

    When USG is a DNS server role, it will check TPR record and itself DNS cache first.

    If without record exist, then will send request to external DNS server.

    You can enter this command to show exist DNS cache exist on DNS server.

    Router> show ip dns server cache 

     

    You can flush PC and USG DNS cache first and capture the packet to make sure how it happened.

    CLI command to flush DNS cache: Router(config)# ip dns server cache-flush

  • IT_Field_Support
    IT_Field_Support Posts: 97  Ally Member
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    Thanks a lot for this information.

    Davy
  • Zyxel_Stanley
    Zyxel_Stanley Posts: 1,366  Zyxel Employee
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    Hi @IT_Field_Support

    After USG setup domain name in System > Host Name.

    DNS server will add a record automatically   (e.g. myrouter.zyxelusg.com -> Interface IP)


    It is for user can easier connecting to WebGUI by entered: https://myrouter.usg.com


    If result IP not belonging to USG LAN interface, then this record is not reply by USG DNS server.

  • IT_Field_Support
    IT_Field_Support Posts: 97  Ally Member
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    Thanks for that information.

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