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Thread: DNS issues

  1. #1
    Join Date
    Mar 2008
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    72

    DNS issues

    We moved to a new server 2 days back an few people report that they're not able to access sites on our server but me and all other staff are able to.. also we randomly used web proxies and its working fine with em too..

  2. #2
    Join Date
    Mar 2005
    Location
    Maine, USA
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    302
    Have them provide traceroutes and pings and if possible DIG outputs. You'll need more troubleshooting data to determine the cause.

  3. #3
    Join Date
    Oct 2004
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    Kerala, India
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    4,750
    Quote Originally Posted by Virtuoso Host View Post
    We moved to a new server 2 days back an few people report that they're not able to access sites on our server but me and all other staff are able to.. also we randomly used web proxies and its working fine with em too..
    There can be issues like this when,

    1.
    Ip of the domain is changed

    2.
    Nameservers of the domain changed.

    3.
    IP of the user blocked inside the server.
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  4. #4
    Join Date
    Sep 2002
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    The most common cause of this sort of problem? You moved servers and didn't allow a proper amount of time for dns propogation.

    Any time you move servers, you should always allow at least 7 days for propogation. I've seen DNS caches take up to 2 weeks, but that's in very rare circumstances.

    Any time you move servers, and change your nameserver IP's, they must be changed at your registrar. This goes for your ip's, your reseller's ip's, and the like. You can't simply move to another server and expect your dns changes to be moved, you need to change those dns ip addresses @ your registrar.

    As others said, get a dnslookup, have the users clear their dns cache (windows and linux), and restart all browsers. This should work for you.
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  5. #5
    You should also note that the ttl of the glue records handed out by the tld servers is 72 hours. This cannot be changed as it is under the control of the tld.

    Thus, when the ip of a nameserver is changed, and a dns cache has cached the name server record *just* before the change, it won't come back for 72 hours.

    This difficulty is best avoided during migrations by using third party dns. This is because the chain of resolution stays unbroken despite the move. The changes are immediately visible at the name server for dns caches querying the records. However, it is necessary that the ttl on the affected records be set at something suitably short *before* the move event. I usually suggest that it be changed down at a time equal to twice the current ttl before the scheduled move, and that the resulting ttl be 5 minutes.
    edgedirector.com
    managed dns global failover and load balance (gslb)
    exactstate.com
    uptime report for webhostingtalk.com

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