DNS and offline servers

Posted on 2007-10-20
Last Modified: 2008-03-10
Dear experts,

I'm not sure I'm looking at things the best way, but here's what I intend to do on a small scale. I have two web servers and a DNS server. They are all about 10 feet away from me and I have complete admin access to them.

I'm planning to take down WebServer A for a few hours, but keep WebServer B online. While I'm doing maintenance on WebServer A, I'd like all requests for it to be answered by WebServer B.

Do I just update DNS records to point to WebServer B and then have them point back to WebServer A when I'm done, or is there a more efficient (perhaps better) way than what I'm thinking of?

The web servers are running Debian 4 and the DNS is running Mac OS X Server.

Thanks in advance!
Question by:jericotolentino
    LVL 7

    Accepted Solution

    Note down the curren TTL of the dns record. Set the TTL of the dns record to a low value, like 60 for a minute or even lower. The lowest possible value is 0 , telling dns server not to cache the record at al.

    Now that you lowered the TTL, wait the time the TTL was before, or if not possible due to time constraints, as long as you can.

    Every server that will request the dns record, will now rerequest it when the record in it's cache is older then the  time specified by the TTL. This way you can make quick changes without waiting for dns server all over the world to catch up.

    You can now do what you suggested: change the ip temporarily to point to the other server.

    Just be sure to put the original TTL back in place after you are done, so your dns server won't get beaten by others with requests for to long.
    LVL 5

    Author Comment

    Thanks for your help! It's simple and works perfectly!

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