Windows 8 and 8.1 Forums

Have to flush DNS cache every few minutes

  1. #1

    Have to flush DNS cache every few minutes

    Toshiba Satelite pro
    Realtek RTL8188CE 802.11n PCI-E NIC
    Drivers checked latest ok

    Since upgrading to Win8.1 , several times an hour I have to /flushdns
    Was fine under Win8.0
    I'm assuming there's some sort of limit to resolver cache size in w8.1 which wasn't there in w8.0
    Either that or it isn't dropping old stuff to make room for new, and refusing to accept new look-ups unless they are cached.
    Or something...
    Family members having same problem with Acer and Dell laptops.
    Lumia 720 on WP8.1 having no trouble at all.

    Is there a way to cure this so it is no longer necessary ?


      My System SpecsSystem Spec

  2. #2

    Central IL
    Posts : 3,468
    Linux Mint 17.2

    You should have no need to flush the dns. Doubtful that there is an issue with Windows 8.x.x for the resolver cache. Most likely you have a Gateway/Router issue. Especially since it is affecting all devices connecting to the network.
      My System SpecsSystem Spec

  3. #3

    Not affecting all devices.
    At this time:
    All Android OK.
    W7 ok
    W8.0 laptop ok
    W8.1 custom build gaming desktop ok.
    WP8.x ok

    Only affecting 3x W8.1 laptops.

    Gateway is a DLink DSL-2642B (DHCP server) via a Billion WiFi.
    DLink is configured to receive primary & secondary DNS resolver IPs from ISP in PPPoA.
    Stable as a rock except for 3x W8.1 laptops - 2 at home & 1 visitor.

    Just for fun, I'm trying some static resolver IPs in the DLink. I'll update thread with results...

      My System SpecsSystem Spec

  4. #4

    Central IL
    Posts : 3,468
    Linux Mint 17.2

    You stated that multiple devices have to be reset for them to have a network connection. Again, your Router is at fault, not the devices. Especially if you are using a router behind a Gateway.
    Last edited by broe23; 24 Oct 2014 at 12:10.
      My System SpecsSystem Spec

  5. #5

    Ok Broe. I'll hunt up another DSL/WiFi router & see how that goes.

    While I'm doing so, can you explain what's happening between the gateway/router & laptop?
    and how it is that flushing the PC DNS cache sorts out the problem?

    This is something I simply cannot get my head around.
    I have a modest understanding of DNS resolver operation, but my OS knowledge is sketchy - more inferred from my knowledge of DNS & TCP...

    When it's broken, Wireshark shows DNS queries outbound and responses containing correct IP addresses from the gateway, even though applications are protesting that they can't access the interwebs. Putting the returned IPs from the Wireshark capture into the browser works just fine.

    Flush DNS & try again : DNS responses identical but the laptop happily generates a SYN...

    So I don't understand why I have to flush the laptop DNS cache before it can use a returned IP to generate a SYN, or how the gateway can be affecting it...

      My System SpecsSystem Spec

  6. #6

    Central IL
    Posts : 3,468
    Linux Mint 17.2

    Never told you to go out and look for another Gateway. Your problem is that if you are using the router behind the DSL Gateway, without having the whole setup properly set up. You are always going to have this problem. If you are only using the D-Link because it has better Wifi, then turn off Wifi on the DSL Gateway, and set the D-Link up as if it would be an Access Point. That would mean turning off its DHCP, assign it a static IP of say and pass through any DHCP assignment from the DSL Gateway. You would connect the D-Link to your gateway by the LAN port on the D-Link, to a LAN port on the Gateway.
      My System SpecsSystem Spec

  7. #7

    Harrisonburg, Va.
    Posts : 10,488
    Windows 8.1.1 Pro with Media Center


    Click image for larger version
      My System SpecsSystem Spec

  8. #8

    Thanks David
    Already running CCleaner.

    Already running the setup you describe.
    The DLink is the DSL gateway & DHCP server. WiFi is off.
    The Billion is WiFi and DHCP relay with static route to gateway.

    Laptop has same issue at work (a technical college).
    Laptop has same issue when plugged into ethernet port of DSL gateway.

    Laptop had no probs at all under W8.0 in either place.
    Started the day I upgraded to W8.1 in both places.
    Only thing that changed is the OS.

    So what is it that W8.1 does differently to W8.0 ?
      My System SpecsSystem Spec

  9. #9

    Central IL
    Posts : 3,468
    Linux Mint 17.2

    If the laptop is having issues on another network, then the laptop is the problem, not the wifi hardware at both locations. As for 8 vs. 8.1. 8.1 fixed some problems, and brought back the desktop option when logging in.
      My System SpecsSystem Spec

  10. #10

    Glad we're finally agreed on that Broe.
    Do you know the nitty griity of how Win8 manages the DNS cache & new DNS look-up results ?
    Can you suggest any registry hack which may change it?
      My System SpecsSystem Spec

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Have to flush DNS cache every few minutes

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