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  1. #1

    Ping can't resolve names; Firefox can

    Iíve just installed Ubuntu Linux, dual booting with Windows XP. My computer is connected to my companyís LAN, which uses ISA as a proxy server.

    My problem is that I cannot resolve names such as whilst pinging from the terminal, but I can enter the same names into Firefox and browse the sites.

    I cannot resolve names for machines on the LAN with ping. Apt-get check fails with a Ďtemporary failure resolving namesí error message and in fact I get this same message when booting (when all the checks are being made). Other programs such as the BitTorrent client fail with the same error. However, during the install process I successfully downloaded the latest security updates for Ubuntu so presumably something was working correctly then.

    My IP is static (there is no DHCP server on the network). On my Windows box the option to specify a gateway and nameserver is selected, but no name or IP is entered (so where is Windows getting its information?). My /etc/resolv.conf contains a nameserver entry with the IP address of the ISA proxy.

    Iím really out of ideas. To be honest I donít understand why Firefox works successfully yet something basic like pinging does not. Any help would be greatly appreciated.

  2. #2
    Linux Engineer
    Join Date
    Apr 2005
    Buenos Aires, Argentina
    How does your /etc/resolv.conf file look like?
    "All the drugs in this world won\'t save you from yourself"

  3. #3
    your firefox is configured to browse thru proxy? :P
    that's what normally happen to me:

    unknown host

    (browse) = no problem


  4. $spacer_open
  5. #4
    Adam, that is exactly what happens to me. apt etc don't work, even if I export the http_proxy variable.

  6. #5
    yeap, a proxy does the dns resolution for you, that's why you're able to browse the net without problem, but an apt-get, yum or ping requires a reachable dns (internal or external). In your case, you're probably blocked from accessing your ISP's dns (as specified in /etc/resolv.conf) or your gateway is not properly configured.

    hmm.... you exported http_proxy.... odd... what does it say if you do a "echo $http_proxy" at shell prompt?

  7. #6
    You have to configure a gateway. In debian read the man page for the interfaces file (man interfaces) to see how to do this. DHCP configres the gateway address for you, but you forgot to do this when you configured your NIC to use a static IP address.

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