All of a sudden I cannot access sites

Discussion in 'Internet Explorer' started by John, Jan 6, 2006.

  1. The problem is that the symptom we are given by IE is inadequate.
    It might really be a problem with your DNS (as the message implies)
    or it might be something else entirely.

    Trace it. Install the XP Pro Support Tools. Use netcap to capture it.
    Install Ethereal (freeware) to format the .cap file. Analyse the trace
    and then you will know what the message really means.


    Robert Aldwinckle
    Robert Aldwinckle, Jan 9, 2006
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  2. John

    John Guest

    Can you tell me where I can download all these programs (Support tool) and
    how do I use Netcap?

    John, Jan 10, 2006
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  3. ....
    You said you have XP Pro? Support Tools are on the product install CD.

    If you have one NIC, to capture all you have to do is enter
    in a cmd window: netcap

    When you are finished recreating the thing you want to capture
    you press Space. The program writes where the capture file is.
    So, right-click, Mark and select and copy that filename to clipboard.
    Then, in Ethereal enter Ctrl-o and paste the filename in. Etc.

    Ethereal, as I mentioned, is freeware with its own site.

    Try a search?

    (MSN search for

    Good luck

    Robert Aldwinckle, Jan 10, 2006
  4. John

    John Guest

    Well, I got all these programs, but I don't really know what I am doing :)

    Thanks any way.
    John, Jan 11, 2006

  5. There is a bit of a learning curve associated with it. <w>

    Have you used netcap yet? Pressed space after invoking it and
    recreating your problem symptom? Copied the filename from
    the cmd.exe display? Opened Ethereal? Used its open dialog?
    Pasted the filename into the open dialog? Opened the .cap file?

    Depending on what your end symptom means you will see different
    combinations of protocols. E.g. if it is strictly a failure of DNS
    that would be the only protocol you would see listed. If it is getting further
    than that (e.g. failing due to a redirect) you would see some HTTP
    request and response exchange(s). The latter can be analysed as text
    by using the Tools menu, Follow TCP Stream command. Etc.

    Even if it does look like the protocols from an expected exchange
    you could check the addresses being used, e.g. in case a hijacker
    was inserting its request first. Etc.

    Post any questions you have if you need more help.

    Good luck

    Robert Aldwinckle, Jan 12, 2006
  6. Sandi Hardmeier - MVP, Jan 17, 2006
  7. John

    John Guest

    Well. nothing happens in is stuck in 0%.
    Using Ethereal, but I am not quite sure what I am seeing. I see a line with
    the "refused" web address, but I don't understand what it tells me...
    John, Jan 19, 2006
  8. John

    John Guest

    I changed the DNS on my computer and I can get to these sites again.

    However, what's strange is:
    1. I've been using these DNS for over a year and everything was fine until
    two weeks ago.
    2. If the DNS is not working, can it be that it is not working "partially"?
    because it's only few sites (4-5) that I cannot access, everything else is
    John, Jan 19, 2006
  9. ....
    Do you have more than one NIC? Do you have to choose one?
    Perhaps you are picking the wrong one?

    If you are trying to make a request and the link is up you should at least
    be able to capture the packets doing that.

    What protocols are listed in your capture?
    If you see HTTP you can use Ethereal's Tools menu
    Follow TCP Stream command to see something readable.
    If it is just a DNS request I don't know if there anything more
    you can do than just look at the request's contents.


    Robert Aldwinckle, Jan 19, 2006

  10. Good. Now you have something solid to notify your ISP about.
    It's their responsibility to make sure their DNS is working properly.

    Sure. It's like you're using a reference book with some pages missing. <w>
    Actually, what should be happening I think is that if your DNS doesn't
    have lookup information already cached it is supposed to request it from
    another server it is connected to and so until the request is either satisfied
    or deemed non-existent. So it may not be your server which is the problem
    exactly but the adjacent servers, etc. Again, that's something for your ISP
    to take care of. Now that you can prove that they have a problem they can't
    just finger-point back to your system.

    If you want you could use nslookup in its interactive mode
    to try to figure out why a request is not being satisfied
    and refine your symptom description even more
    but that shouldn't be necessary to get them working
    on a fix.

    Alternatively you may get better help from a newsgroup which specializes
    in networking for your OS. Here's a troubleshooter which contains a link
    to one for followup questions:

    Good luck

    Robert Aldwinckle, Jan 19, 2006
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