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Thread: server DNS address could not be found

  1. #1

    Default server DNS address could not be found

    Hi,

    having updated to 42.2 leap version, I get this error connecting to a webserver:

    This site can’t be reached

    fastmail.fastwebnet.it’s server DNS address could not be found.



    ERR_NAME_NOT_RESOLVED


    how can i fix it ?

    Regards,

    MC









  2. #2
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    Default Re: server DNS address could not be found

    You do not explain how you try to connect to that system. Using some browser? Please take note of the fact that we can not look over your shoulder what you are doing. We depend on your complete description on what you do and what happens.

    Can you resolve other host/domain names or is this the only one?
    What is/are your DNS server(s)?
    Code:
    grep -v '^#' /etc/resolv.conf
    I can resolve it:
    Code:
    henk@boven:~> nslookup fastmail.fastwebnet.it
    Server:         194.109.6.66
    Address:        194.109.6.66#53
    
    Non-authoritative answer:
    Name:   fastmail.fastwebnet.it
    Address: 85.18.95.157
    
    henk@boven:~>
    And when I use Firefox to connect to it, there is a connection, but it is redirected to
    Code:
    http://www.fastweb.it/servizi/fastmail/
    Henk van Velden

  3. #3
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    Default Re: server DNS address could not be found

    When an Internet name cannot be resolved...

    - You don't have a Hosts file that can provide resolution
    - The name isn't in the DNS cache of the DNS server you're pointing to. Depending on how that DNS server is configured, it might just refuse to do anything further(sometimes this is the case using a private DNS server). If you're pointing to a public DNS server provided by an ISP somewhere on the Internet and it can be the ISP providing your Internet service, then the unresolved request can be forwarded to another DNS which will look in its own cache, and if a resolution doesn't exist then the request can be forwarded again to another DNS server and this gets repeated until a DNS server has an answer... And then the result is passed down the same chain of DNS servers in reverse until it can reach you.

    The problem is that if your DNS query is passed along a chain of multiple DNS servers and sometimes subject to timeouts, it can take a long time for the name to be resolved and the result returned back to you, and by then your original request may itself have timed out and you see the error you see.

    When this happens, then simply wait a couple minutes and try the network connection again. You will then get a name resolution result that was created by your previous attempt.

    This should only happen if you try to connect to a little used URL not visited by anyone else using your DNS server in a long time, if ever. Popular websites will always work because you're following along behind someone else who requested name resolution for that site recently.

    The alternative to waiting and trying again as I described above is to point your machine to different DNS, you can point to a bigger ISP or Google. Interestingly, I just took a look around and I think that public DNS servers may no longer be defined as "Tier 1" for multi-machine/networks(setting up your own forwarding DNS) and "Tier 2" for individual client machines. Maybe because nowadays, bandwidth and computing power is so cheap there is no longer a need to differentiate...
    But you can Google something like "public DNS servers" to see listings of plenty of machines. Be careful what you point to though, it should be something well known and trusted like Google or the opennic project to lessen the chance you'd become a victim of "DNS poisoning" where someone maliciously resolves a wrong address.

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  4. #4

    Default Re: server DNS address could not be found

    Quote Originally Posted by hcvv View Post
    You do not explain how you try to connect to that system. Using some browser? Please take note of the fact that we can not look over your shoulder what you are doing. We depend on your complete description on what you do and what happens.

    Can you resolve other host/domain names or is this the only one?
    What is/are your DNS server(s)?
    Code:
    grep -v '^#' /etc/resolv.conf
    I can resolve it:
    Code:
    henk@boven:~> nslookup fastmail.fastwebnet.it
    Server:         194.109.6.66
    Address:        194.109.6.66#53
    
    Non-authoritative answer:
    Name:   fastmail.fastwebnet.it
    Address: 85.18.95.157
    
    henk@boven:~>
    And when I use Firefox to connect to it, there is a connection, but it is redirected to
    Code:
    http://www.fastweb.it/servizi/fastmail/
    Code:
    I run the first script:
    
    studio@linux:~> grep -v '^#' /etc/resolv.conf
    search fastwebnet.it site
    nameserver 192.168.1.254
    nameserver 62.101.93.101
    nameserver 83.103.25.250
    studio@linux:~> 
    
    and the second one:
    
    tudio@linux:~>  nslookup fastmail.fastwebnet.it
    Server:         192.168.1.254
    Address:        192.168.1.254#53
    
    
    ** server can't find fastmail.fastwebnet.it: NXDOMAIN
    
    I use chrome browser and a wifi connection.
    
    Regards,
    
    MC

  5. #5
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    Default Re: server DNS address could not be found

    You forgot to answer the question if this is the only one you can resolve other host/domain names.

    Your configuration looks OK. That is, it has your router as the first DNS server. This means that if that one is not functioning correct, you have a problem.

    The output of the second command shows that the router's DNS functions, but can not resolve the address (where my server can).

    The other two servers in the list are anyres1.fastwebnet.it and anyres2.fastwebnet.it. You could try to move your router at the end of the three, to see if that helps. It will then go to anyres1.fastwebnet.it

    Another test would be to replace the three lines with
    Code:
    nameserver 8.8.8.8
    That is a DNS server from Google that is known to work correct.

    BTW. You should only put your copied/pasted computer text between the CODE tags, not your explanations.
    Henk van Velden

  6. #6
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    Default Re: server DNS address could not be found

    Quote Originally Posted by MarcoC View Post

    I run the first script:
    Code:
    studio@linux:~> grep -v '^#' /etc/resolv.conf
    search fastwebnet.it site
    nameserver 192.168.1.254
    nameserver 62.101.93.101
    nameserver 83.103.25.250
    studio@linux:~>
    and the second one:

    Code:
    tudio@linux:~>  nslookup fastmail.fastwebnet.it
    Server:         192.168.1.254
    Address:        192.168.1.254#53
    
    
    ** server can't find fastmail.fastwebnet.it: NXDOMAIN
    I use chrome browser and a wifi connection.

    Regards,

    MC
    You can test your DNS before changing your settings using nslookup.

    So, for instance,
    The default DNS server is your the DNS in your private LAN (192.168.1.254) which is failing either because it's not configured correctly or has forwarded your query upstream but not net received a response (see my previous post).
    You can immediately and temporarily change your DNS server with the command "server <ip address" as follows (hit "return" immediately after nslookup so you're not running a single-use compound command. At any time you can type "quit" to exit back to your normal console)
    Code:
    nslookup
    > server 62.101.93.101
    > fastmail.fastwebnet.it
    And then you should see the result from your newly specified DNS server.

    Once you've determined a good working DNS server,
    Then you can change your DNS order although I suspect that your current network configuration is automatic.

    TSU
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