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Creating PTR Records on a Shared IP

Discussion in 'General Discussion' started by computerhouse, Oct 3, 2008.

  1. computerhouse

    computerhouse Registered

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    Is it possible to create PTR records for different domains that are shared by the same IP?
    I know how to add them in CPanel, but the fact that more than one would point to the same IP causes an issue.

    Thanks,
    CompHouse
     
  2. sparek-3

    sparek-3 Well-Known Member

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    A PTR record can only point back to one hostname.

    Typically with a shared IP, you set the reverse DNS on the shared IP to the server's hostname, such that that IP reverses back to the hostname and the hostname resolves to that IP.

    IP addresss --> Hostname

    Hostname --> IP address

    This will satisfy the reverse DNS set up required by many mail servers.
     
  3. computerhouse

    computerhouse Registered

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    Sorry I'm a noob at this

    In Cpanel,
    Add New Entries
    ____________ 14400 IN PTR HOSTNAME

    So I would put the Shared IP in the first line, and then my mailserver name in the hostname area?

    65.x.x.x 14400 IN PTR MAIL.DOMAINNAME.COM ?

    Thanks for your help.

    Comphouse
     
  4. sparek-3

    sparek-3 Well-Known Member

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    Its doubtful that you have delegation access for creating a PTR record for that IP address. Generally you contact the datacenter where you are hosting the server at, or the company in charge of giving you that IP address and ask them to set up the reverse DNS entry.
     
  5. frame25

    frame25 Registered

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    I have such delegation access and need the same question answered. Would someone be willing to post an example of getting this scenario properly working?

    Let's say my main server IP is 1.1.1.1 (server.example.com), and my main shared IP is 1.1.1.2, on which I am running example.com, example2.com, and example3.com. What would I do and how would I set up rDNS for this scenario?

    Thank you in advance for anyone who can help!
     
  6. markb14391

    markb14391 Well-Known Member

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    I'm not sure if you can properly do rDNS for multiple entries on the same IP. You might need dedicated IPs to accomplish what you're trying to do.

    Just curious...do you really need rDNS for all the domains on that IP? If it's just for e-mail purposes, you might only need a PTR entry for the main hostname on the IP. For example, on one cPanel installation I gave my main hosting account (as a reseller) a dedicated IP, with a hostname that has rDNS. I set it so that all shared-IP accounts created under that account use the same IP, and that e-mail is sent from the account's IP. I don't need to set PTR for all of those domains, because the e-mail goes through the hostname and is accepted properly because of that.

    So, if the master account is myreselleraccount.com, and I create subaccount1.com, subaccount2.com and subaccount3.com, I just set PTR for the hostname host.myreselleraccount.com. Mail for the sub-accounts is routed through that host and is accepted by other mail hosts because the rDNS is set up properly on the reseller account.

    Hope that helps. If it doesn't, please ignore. ;-)
     
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