can i have 2 IPs with the same PTR record?

omg 1 Reputation point
2022-09-13T12:43:15.58+00:00

Hello, can I have 2 IPs with the same PTR Record?

example:

122.122.122.1 with PTR Record mail.mydomain.com
122.122.122.2 with PTR Record mail.mydomain.com

each IP address is with different ISP, the purpose for this is because im running a email server with one IP but here in my country sometimes the internet service providers falls and keep fall about 1-2 days , so the plan is , when one ISP falls I could use the IP from the other ISP.

is this possible to have same PTR Record in two different IPs?

Thanks!

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Exchange Server Management
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  1. Andy David - MVP 140.8K Reputation points MVP
    2022-09-13T14:55:55.903+00:00

    You can do that but not recommended:
    https://serverfault.com/questions/618700/why-multiple-ptr-records-in-dns-is-not-recommended

    This expectation is reflected in software that does reverse lookups; often such software specifically expects a single name back and it expects to be able to use that name as a canonical name for that host. If there are multiple names returned it's common to just take one at random because they have absolutely no way of knowing which one you would have preferred for this particular occasion.

    As the general expectation is that there is one canonical name associated with an IP address and that name is what the PTR should point to, adding multiple names generally has no upside (nothing expects any random A/AAAA record to have a matching PTR) but it has a potential downside as it can cause strange results as you have no control over which of your PTR records will be used if you have added more than one.

    In essence, if you have multiple PTR records you do not actually make your host appear more legitimate but rather the opposite, you run the risk of failing some validation or otherwise breaking something.

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