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A Record

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  • 12-02-2007 1:20pm
    #1
    axer
    Registered Users Posts: 5,517 ✭✭✭


    Hi Y'all,

    Just a quick question.

    I want to change the webhosting currently hosting a website. The email is already being handled locally so I just want to change the DNS records for the website only.

    Am I correct in thinking that I only need change the A Record of the domain to point to the new web host?

    Thanks for any help/advice.


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    #2
    stakey
    Registered Users Posts: 721 ✭✭✭stakey


    yup, that's pretty much it... watch out for propagation of course :D


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    #3
    axer
    Registered Users Posts: 5,517 ✭✭✭axer


    deconstruct wrote:
    watch out for propagation of course :D
    ??


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    #4
    stakey
    Registered Users Posts: 721 ✭✭✭stakey


    When you change the IP address that the A record is pointing to it will take probably at max 24 hours before all ISP's etc on the internet update there own records to match that of your DNS hosts...

    From what your saying though it should be grand. For some time some ISP's will point users to the old records and then eventually change over (within that '24 hour' period).


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    #5
    axer
    Registered Users Posts: 5,517 ✭✭✭axer


    deconstruct wrote:
    When you change the IP address that the A record is pointing to it will take probably at max 24 hours before all ISP's etc on the internet update there own records to match that of your DNS hosts...

    From what your saying though it should be grand. For some time some ISP's will point users to the old records and then eventually change over (within that '24 hour' period).
    ok, wasnt sure what you meant.

    Thanks.


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    #6
    mick.fr
    Closed Accounts Posts: 1,974 ✭✭✭mick.fr


    deconstruct wrote:
    When you change the IP address that the A record is pointing to it will take probably at max 24 hours before all ISP's etc on the internet update there own records to match that of your DNS hosts...

    From what your saying though it should be grand. For some time some ISP's will point users to the old records and then eventually change over (within that '24 hour' period).


    Not exacly, change is immediate and usually a simple (or several) F5 in your browser will redirect you immediately to the new website.
    Your usual ISP do not store other DNS Server entries, a part from cache, for a limited time only, or unless your ISP is actually hosting your DNS Domain name. In that case it is the authoritative DNS Server for your domain and all resolution queries will be directed to it.

    A www rentry should also be there.
    A entry for a website is techically working, but not enough (RFC compliance).

    This 24/48/72 hours statement is only true when a new domain name is aquired and propagated to the root servers and below.


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    #7
    phil
    Registered Users Posts: 568 ✭✭✭phil


    Mick, sorry, you need to read up more on DNS caching or explain yourself a little better. ISPs will cache domain A record lookups. Although, the person operating the nameservers can change the TTL in most cases, they're unaware of this.

    86400 is a sane commonly used default for a TTL, which is 24 hours. The TTL can be much higher, or much lower.

    Low TTLs are not recommended and with a busy website, your DNS hosts nameservers can end up being hammered with DNS requests. If you need to lower your TTL, do so temporarily and up it back up again afterwards.

    Regards,

    Phil.


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    #8
    mneylon
    Registered Users Posts: 7,739 ✭✭✭mneylon


    Mick

    Unless the TTL is 0 it is not an instant update. Even if the TTL is set really low some ISPs caching nameservers will cache for 24 hours anyway to save on lookups.

    There's a reasonably non-technical explanation of how it all works here:

    http://en.wikipedia.org/wiki/Domain_name_system#DNS_in_practice

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