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Thread: Very Slow DNS Resolution

  1. #1
    Join Date
    Apr 2009
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    Question Very Slow DNS Resolution

    Hi,

    first, as this is my first post, I want to say how much I appreciate the help offered in these forums. I have used the Information very often so far but never had to register to ask a questions because all the answers were already here

    But now I have a problem which I couldn't resolve with the information I found so far:

    My DNS resolution is very slow. Even though Pings are as fast (or only marginally slower) as usual and I can use the full speed of my connection (DSL in Switzerland). I have changed the DNS Settings (to the OpenDNS Servers) in the NetworkManager and afterwards on the Router, it didn't help. I also used a different browser (than Firefox) and deactivated IPv6 to be on the safe side but the resolving of Domain Names still takes around 2-4s or even longer.

    I have this issue since Saturday but can't really say if it is in connection with an Update.

    Many thanks in advance, best,

    Marcus

  2. #2
    Join Date
    Nov 2005
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    Re: Very Slow DNS Resolution

    I've noticed a strange behaviour when using NetworkManager via a DHCP connection (wired or wireless).

    NetworkManager assigns two DNS addresses - the first being 192.168.0.1 (my wireless router), and the second being the first actual DNS address as configured within my router.

    Try editing your connection in NetworkManager, and change from DHCP to (I think) "DHCP addresses only", and manually enter your DNS address to either a) only your router's address, or b) only your ISP's/openDNS addresses.

  3. #3
    Join Date
    Oct 2005
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    169

    Re: Very Slow DNS Resolution

    this might the be the ipv6 dns bug that some routers have, try to disable ipv6

  4. #4
    Join Date
    Apr 2009
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    11

    Re: Very Slow DNS Resolution

    Thanky for the fast answers!

    I tried this by setting it manually to the adress of my router (before I had already entered the OpenDNS adresses this way) and it didn't help.

    I already deactivated IPv6 according to this short tutorial: http://ubuntuforums.org/showpost.php...6&postcount=42

    Best,

    Marcus

  5. #5
    Join Date
    Apr 2009
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    Re: Very Slow DNS Resolution

    Anybody have another idea?

  6. #6
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    Re: Very Slow DNS Resolution

    How does one time the dns resolution?

  7. #7
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    Apr 2009
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    11

    Re: Very Slow DNS Resolution

    Maybe its naive from my side, but when I try to ping it takes a while until it shows the IP (unusualy long) something or load a Website it shows "Looking up x" very long which leads me to conclude that the computer has a problem in resolving the Domain into an IP address.

    Best,

    Marcus

  8. #8
    Join Date
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    Re: Very Slow DNS Resolution

    Quote Originally Posted by marcuskuhn View Post
    Maybe its naive from my side, but when I try to ping it takes a while until it shows the IP (unusualy long) something or load a Website it shows "Looking up x" very long which leads me to conclude that the computer has a problem in resolving the Domain into an IP address.

    Best,

    Marcus
    I happens to me as well. I suspected that perhaps the MTU may impact lookup times, but lowering the MTU value didn't help for me (perhaps the MTU doesn't impact DNS resolution anyway).

    What router model/firmware do you use? It may be a factor. I'm using a D-Link DI-524, B4 revision with firmware 2.07. I don't see this slow resolution in Windows XP, Vista or Windows 7.

  9. #9
    Join Date
    Apr 2009
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    11

    Re: Very Slow DNS Resolution

    I don't have another OS installed, but my Netbook which is running the Jaunty NBR and which I didn't update in the last week doesn't have the problem. Neither on WLAN nor on cable. My Router is the one provided by my ISP, a netopia 3397GP ADSL2 Router.

    To further confirm the problem is related to DNS, when I enter an IP-Adress directly, browsing is as fast as usual.

  10. #10
    Join Date
    Oct 2007
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    Germany
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    46

    Re: Very Slow DNS Resolution

    take a look at /etc/resolv.conf and play with the servers and see if it makes a difference

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