DNS Problem - Networking

This is a discussion on DNS Problem - Networking ; Hi, I am using Fedora 8. Its my impression that the DNS servers listed in /etc/resolv.conf are the ones always used for name lookup. The resolv.conf file generated when I installed F8 is: ------------------------------------- ; generated by /sbin/dhclient-script search domain.actdsltmp ...

+ Reply to Thread
Results 1 to 6 of 6

Thread: DNS Problem

  1. DNS Problem

    Hi,

    I am using Fedora 8.

    Its my impression that the DNS servers listed in /etc/resolv.conf are the
    ones always used for name lookup.

    The resolv.conf file generated when I installed F8 is:

    -------------------------------------
    ; generated by /sbin/dhclient-script
    search domain.actdsltmp
    nameserver 192.168.0.1
    nameserver 208.42.42.42
    -------------------------------------

    I am not sure why 192.168.0.1 is there since it is my gateway address. I
    manually edited resolv.conf to reflect the DNS servers given to me by my
    ISP. The edited one is:

    -------------------------------------
    ; generated by /sbin/dhclient-script
    search domain.actdsltmp
    nameserver 209.98.98.98
    nameserver 208.42.42.42
    -------------------------------------

    When I restart my computer, the resolv.conf file goes back to the "just
    installed" version. My ActionTec DSL modem was manually configured to
    know about the two DNS servers given by my ISP but this has no affect.

    Occasionally I get problems which appear to be DNS related but I am not
    sure. In any case, I think I should have both DNS servers available.

    My question is how do I get resolv.conf to reflect both my DNS servers?

    Here is some more information.

    1. I have my network (/etc/sysconfig/network-scripts/ifcfg-eth0)
    configured to use DHCP rather than a static IP.

    2 I turned off NetworkManager and NetworkManagerDispatcher and turned on
    network, i.e.

    [joe@sam02 ~]$ /sbin/chkconfig --list | grep Network
    NetworkManager 0ff 1ff 2n 3ff 4ff 5ff 6ff
    NetworkManagerDispatcher 0ff 1ff 2ff 3ff 4ff
    5ff 6ff

    [joe@sam02 ~]$ /sbin/chkconfig --list | grep network
    network 0ff 1ff 2ff 3n 4n 5n 6ff

    I am not sure what NetworkManager and NetworkManagerDispatcher do, the
    "man" pages were not helpful.

    3. As soon as I installed F8 I pointed my /etc/yum.repos.d files to
    point to my local yum server. I did this since I have several F8
    machines and it is easier to use a local yum server. This is probably
    not relevant.

    4. I have another F8 computer which uses a static IP and I don't have
    this problem with resolv.conf.

    I thank you for reading this and any help you can give me.

    Joe Hesse

  2. Re: DNS Problem

    Joseph Hesse wrote:
    > Hi,
    >
    > I am using Fedora 8.
    >
    > Its my impression that the DNS servers listed in /etc/resolv.conf are the
    > ones always used for name lookup.
    >
    > The resolv.conf file generated when I installed F8 is:
    >
    > -------------------------------------
    > ; generated by /sbin/dhclient-script
    > search domain.actdsltmp
    > nameserver 192.168.0.1
    > nameserver 208.42.42.42
    > -------------------------------------
    >
    > I am not sure why 192.168.0.1 is there since it is my gateway address. I
    > manually edited resolv.conf to reflect the DNS servers given to me by my
    > ISP.


    DHCP servers normally tell their clients the address of DNS servers and
    it is normal for gateway/firewall/routers to run DNS servers themselves.
    If you set up the DNS on your gateway correctly, everything should work OK.

    Robert

    The edited one is:
    >
    > -------------------------------------
    > ; generated by /sbin/dhclient-script
    > search domain.actdsltmp
    > nameserver 209.98.98.98
    > nameserver 208.42.42.42
    > -------------------------------------
    >
    > When I restart my computer, the resolv.conf file goes back to the "just
    > installed" version. My ActionTec DSL modem was manually configured to
    > know about the two DNS servers given by my ISP but this has no affect.
    >
    > Occasionally I get problems which appear to be DNS related but I am not
    > sure. In any case, I think I should have both DNS servers available.
    >
    > My question is how do I get resolv.conf to reflect both my DNS servers?
    >
    > Here is some more information.
    >
    > 1. I have my network (/etc/sysconfig/network-scripts/ifcfg-eth0)
    > configured to use DHCP rather than a static IP.
    >
    > 2 I turned off NetworkManager and NetworkManagerDispatcher and turned on
    > network, i.e.
    >
    > [joe@sam02 ~]$ /sbin/chkconfig --list | grep Network
    > NetworkManager 0ff 1ff 2n 3ff 4ff 5ff 6ff
    > NetworkManagerDispatcher 0ff 1ff 2ff 3ff 4ff
    > 5ff 6ff
    >
    > [joe@sam02 ~]$ /sbin/chkconfig --list | grep network
    > network 0ff 1ff 2ff 3n 4n 5n 6ff
    >
    > I am not sure what NetworkManager and NetworkManagerDispatcher do, the
    > "man" pages were not helpful.
    >
    > 3. As soon as I installed F8 I pointed my /etc/yum.repos.d files to
    > point to my local yum server. I did this since I have several F8
    > machines and it is easier to use a local yum server. This is probably
    > not relevant.
    >
    > 4. I have another F8 computer which uses a static IP and I don't have
    > this problem with resolv.conf.
    >
    > I thank you for reading this and any help you can give me.
    >
    > Joe Hesse


  3. Re: DNS Problem

    Joseph Hesse writes:

    > Hi,
    >
    > I am using Fedora 8.
    >
    > Its my impression that the DNS servers listed in /etc/resolv.conf are the
    > ones always used for name lookup.
    >
    > The resolv.conf file generated when I installed F8 is:
    >
    > -------------------------------------
    > ; generated by /sbin/dhclient-script
    > search domain.actdsltmp
    > nameserver 192.168.0.1
    > nameserver 208.42.42.42
    > -------------------------------------
    >
    > I am not sure why 192.168.0.1 is there since it is my gateway address. I
    > manually edited resolv.conf to reflect the DNS servers given to me by my
    > ISP. The edited one is:
    >
    > -------------------------------------
    > ; generated by /sbin/dhclient-script
    > search domain.actdsltmp
    > nameserver 209.98.98.98
    > nameserver 208.42.42.42
    > -------------------------------------
    >
    > When I restart my computer, the resolv.conf file goes back to the "just
    > installed" version. My ActionTec DSL modem was manually configured to
    > know about the two DNS servers given by my ISP but this has no affect.
    >
    > Occasionally I get problems which appear to be DNS related but I am not
    > sure. In any case, I think I should have both DNS servers available.
    >
    > My question is how do I get resolv.conf to reflect both my DNS servers?


    Suppose your modem is on the "eth0" interface. Then you would set up
    a file called "/etc/dhclient-eth0.conf". It would have a line like
    this in it:

    supersede domain-name-servers 209.98.98.98, 208.42.42.42;

    You might also want to supersede the search line, if there's anything
    that makes more sense. Read "man dhclient.conf" for the details on
    what can go into this file.

    > Here is some more information.
    >
    > 1. I have my network (/etc/sysconfig/network-scripts/ifcfg-eth0)
    > configured to use DHCP rather than a static IP.
    >
    > 2 I turned off NetworkManager and NetworkManagerDispatcher and turned on
    > network, i.e.
    >
    > [joe@sam02 ~]$ /sbin/chkconfig --list | grep Network
    > NetworkManager 0ff 1ff 2n 3ff 4ff 5ff 6ff
    > NetworkManagerDispatcher 0ff 1ff 2ff 3ff 4ff
    > 5ff 6ff
    >
    > [joe@sam02 ~]$ /sbin/chkconfig --list | grep network
    > network 0ff 1ff 2ff 3n 4n 5n 6ff
    >
    > I am not sure what NetworkManager and NetworkManagerDispatcher do, the
    > "man" pages were not helpful.


    Use NetworkManager on a computer that you want to connect to different
    networks at different times, depending on what networks are available.
    This is really useful on a laptop with a wireless network adapter.

    NetworkManagerDispatcher allows you to run scripts based on what
    network you've connected to. It doesn't do anything in the default
    configuration, but you could use it to do additional initialization.

    Scott
    --
    Scott Hemphill hemphill@alumni.caltech.edu
    "This isn't flying. This is falling, with style." -- Buzz Lightyear

  4. Re: DNS Problem

    Scott Hemphill writes:

    > Joseph Hesse writes:
    >
    >> Hi,
    >>
    >> I am using Fedora 8.
    >>
    >> Its my impression that the DNS servers listed in /etc/resolv.conf are the
    >> ones always used for name lookup.
    >>
    >> The resolv.conf file generated when I installed F8 is:
    >>
    >> -------------------------------------
    >> ; generated by /sbin/dhclient-script
    >> search domain.actdsltmp
    >> nameserver 192.168.0.1
    >> nameserver 208.42.42.42
    >> -------------------------------------
    >>
    >> I am not sure why 192.168.0.1 is there since it is my gateway address. I
    >> manually edited resolv.conf to reflect the DNS servers given to me by my
    >> ISP. The edited one is:


    Your modem/router may have a caching name server running on it. I
    just helped a friend with his ADSL modem. The only name server that
    showed up in /etc/resolv.conf was 192.168.1.1. It resolved names just
    fine. You could make sure that it is working by removing the
    208.42.42.42 line. Then, if you want, you could append a third name
    server to the configuration using /etc/dhclient-eth0.conf.

    [snip]

    Scott
    --
    Scott Hemphill hemphill@alumni.caltech.edu
    "This isn't flying. This is falling, with style." -- Buzz Lightyear

  5. Re: DNS Problem

    On Mon, 25 Feb 2008, in the Usenet newsgroup comp.os.linux.networking, in
    article <13s5kbhiuv5v68@corp.supernews.com>, Joseph Hesse wrote:

    >Its my impression that the DNS servers listed in /etc/resolv.conf are
    >the ones always used for name lookup.


    With the exception of DNS query tools like 'dnsquery', 'dig', 'host'
    and 'nslookup' which _can_ be told to use other name servers as an
    option, that's basically correct.

    >The resolv.conf file generated when I installed F8 is:
    >
    >-------------------------------------
    >; generated by /sbin/dhclient-script


    Actually, it's not the file generated by the install program, but the
    file generated by your DHCP client every time you boot.

    >search domain.actdsltmp
    >nameserver 192.168.0.1
    >nameserver 208.42.42.42
    >-------------------------------------
    >
    >I am not sure why 192.168.0.1 is there since it is my gateway address.


    Because that's the addresses specified by your DHCP server, and you
    have configured your DHCP client to overwrite the existing file.

    >I manually edited resolv.conf to reflect the DNS servers given to me
    >by my ISP. The edited one is:
    >
    >-------------------------------------
    >; generated by /sbin/dhclient-script
    >search domain.actdsltmp


    man 5 resolver and see if that line is appropriate. Usually, it's not.

    >When I restart my computer, the resolv.conf file goes back to the "just
    >installed" version.


    No, it's going to the values handed out by your DHCP server.

    >My ActionTec DSL modem was manually configured to know about the two
    >DNS servers given by my ISP but this has no affect.


    Not enough details. Is the DSL modem operating a name server? Use one
    of those four tools above to query the modem asking about an internal
    as well as external hostname. Does the modem supply the answer or not?

    >Occasionally I get problems which appear to be DNS related but I am not
    >sure. In any case, I think I should have both DNS servers available.


    The resolver believes the first answer it receives. If you ask the DNS
    about internal hosts - such as 'poobah', the resolver will attempt to
    figure out a "full" name, and ask the name server[s] about that (such
    as 'poobah.example.com'). Because you have the 'search' directive, it
    will then try 'poobah.domain.actdsltmp' and
    'poobah.example.com.domain.actdsltmp' - neither of which are likely to
    resolve. The name server will return a NXDOMAIN error, and that's the
    end of the querys. It does not matter if the "other" name server knows
    the correct answer - because the first name server that answered said
    the name isn't valid.

    Any name server you list should be able to answer ALL questions. If
    you have a local domain setup, the normal technique is to point your
    systems at a/the name server[s] that can answer queries about that
    domain, and have the name server (not your clients) forward unknown
    queries to an outside name server, or have it recursively resolve
    the name by performing a normal name search on it's own. This is
    detailed in the DNS-HOWTO.

    >1. I have my network (/etc/sysconfig/network-scripts/ifcfg-eth0)
    >configured to use DHCP rather than a static IP.


    If your computer isn't moving from network to network, DHCP may be a
    larger problem than it's worth.

    >3. As soon as I installed F8 I pointed my /etc/yum.repos.d files to
    >point to my local yum server. I did this since I have several F8
    >machines and it is easier to use a local yum server. This is probably
    >not relevant.


    Correct to both statements.

    >4. I have another F8 computer which uses a static IP and I don't have
    >this problem with resolv.conf.


    Yes, it's not running the DHCP client which has been set to overwrite
    the various system files.

    Old guy

  6. Re: DNS Problem

    On Mon, 25 Feb 2008 14:32:17 +0000, Joseph Hesse wrote:

    > Hi,
    >
    > I am using Fedora 8.


    > I thank you for reading this and any help you can give me.
    >
    > Joe Hesse


    Your router will act as a DNS nameserver, and whatever nameservice it
    doesn't have cached in it will then be provided by the upstream
    nameserver, which in your case is 209.98.98.98, etc.

    Be advised that my experience with the ActionTec modems on flakyQuest DSL
    service is that if your OS or your browser default to IPv6, you'll
    encounter several seconds (up to 20 or more) of delay before your system
    then reverts and attempts IPv4 DSN nameservice, and so you'll always be
    encountering SLOW nameservice.

    The (best) solution is to globally disable IPv6 on your OS. Alternately,
    you can disable IPv6 in your Firefox, but this will mean that all other
    nameservice will remain slow. Different distros can disable IPv6 through
    different means, but this generally involves a config file for your
    networking setup. Example: in Mepis, edit your

    /etc/modprobe.d/aliases file to change line:

    alias net-pf-10 ipv6 change to:
    alias net-pf-10 off


    and add this line below it:
    alias ipv6 off and then save the file. restart your networking and
    you now have IPv6 disabled globally.

    In Firefox, type in the URL bar: about:config

    Then search for config line:
    network.dns.disableIPv6 then right click that line, and select "toggle"
    to change it to "true"

    These changes should spruce up your nameservice when using the ActionTek
    modem on Quest DSL, and perhaps on other providers as well. That modem
    just seems to choke on IPv6, or it might just be Quest's nameservers which
    choke on it.

    Regards,
    vg


+ Reply to Thread