PC's using the same modem are pointing to different IP's for the same website.

Posted on 2007-07-30
Last Modified: 2010-05-18
We just switched our NS from our dedicated GoDaddy server back to our Dedicated Linux server.
The switch took place at 3am this morning.
Almost all PC's we have tested have our website going to the correct Linux website.

But we have one broker, who has multiple PC's in her house, but they all connect to the internet through 1 modem.  1/2 of her PC's (when they ping and bring up the site) point to GoDaddy and the other 1/2 point to valueweb.

Is that "normal" and something that will resolve itself?
Or is there something I can do to help her odd man out PC's connect to the right site?
Thank You
Question by:CyberRazz32
    LVL 8

    Accepted Solution

    She should compare her DNS setting on each PC.   It is likely that they are configured differently.

    LVL 24

    Expert Comment

    >> Is that "normal" and something that will resolve itself?

    Yes. Depending on the broker's ISP, it may take 24-48 hours to be resolve, but it will eventually change as long as no PC or local nameserver on the broker's network has a manual entry set up to point '' to your old IP.

    >> Or is there something I can do to help her odd man out PC's connect to the right site?

    Yes. Try to clear the DNS cache on the affected machines, or on the proxy server that they use. On Windows boxes, you can use:
     ipconfig /flushdns

    On a Mac:
     lookupd -flushcache

    On Linux:
     Restart the nscd daemon using a command like `/etc/rc.d/init.d/nscd restart`.

    Author Comment

    We tried ipconfig /flushdns on her PC, but that did not work.
    Is there a way to check "PC or local nameserver on the broker's network has a manual entry set up to point '' to your old IP."?
    LVL 24

    Expert Comment

    To see if any manually-created entries exist, check the hosts file on your systems.

    On a Windows computer, check for a file named 'hosts' in the following locations:
     Windows Vista        =        C:\WINDOWS\SYSTEM32\DRIVERS\ETC
     Windows XP       =       C:\WINDOWS\SYSTEM32\DRIVERS\ETC
     Windows 2K       =       C:\WINNT\SYSTEM32\DRIVERS\ETC
     Win 98/ME       =       C:\WINDOWS

    On a Linux computer, the file will be located at /etc/hosts

    Edit the host file and look for any entry that references your website. Delete the entry if it exists.

    Repeat for any proxy server on the network. You may need to contact the broker's network administrator to determine if a proxy is being used.
    LVL 4

    Expert Comment

    You can try and flush the ARP (Address Resolution Protocol) Caches using the command "arp -d" from command prompt.  Alternatively, you can attempt to repair the connection by right-clicking on the connection icon in the tray and selecting repair.

    But usually, DNS changes take 24-48 hours to propogate as stated above.

    Author Comment

    This is probably a stupid question.

    But is it normal for the IP for a website to be different for different users during a DNS change (so it goes in waves), and not everybody changes at the same time.

    I just want to verify that is correct, and I don't sit and wait the 48 hrs in case it is something different.
    LVL 24

    Expert Comment

    Yes, that is a normal behavior. DNS is a distributed system, so when you updated your IP address, it takes a while for all of the nodes (DNS servers) to get information about your new address. All DNS servers do not get updated information on a real-time basis, because that would take an incredible amount of bandwidth. Instead, each DNS server requests updates on an administrator-defined schedule. Some DNS servers update every four to six hours, while others updated only once every day or so.

    Author Comment

    Thanks for all your help, you have all been very insite full.
    One final question and then I will be done.

    Is there somewhere you can go (maybe a website) or an application you can run, so you can verify when your IP has been updated on all the DNS servers?
    LVL 24

    Expert Comment

    Unfortunately, no. The reason is, that would require that the application in question query every DNS server on the internet. I supposed someone could write such an application, but tracking every available DNS server (there are tens of thousands) would be a monumental task.

    You can, however, check your DNS information at various online locations to get an overview of what *some* of the internet is seeing. For example, try sites like

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