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Very simple question that I can't find a reliable answer to, with Google -- can my server be the reverse DNS for multiple IP addresses?

Is it bad practise / wrong / asking for trouble to say my server sub.hostname.co.uk is the rDNS for:

118.168.10.100

and

118.168.11.200

NOTE: These IP addresses are in different subnets (.10. and .11. )

This Q&A seems to imply it would cause awkwardness. To clarify further, the second IP is a secondary IP, if that changes the requirement criteria.

Each Site on the server will be associated primarily with one of the two IPs.

?? Thanks!

Martin
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1 Answers1

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I would say it depends. If we look at how rDNS works there is no problem. The resolver asks for example 78.67.45.123.in-addr.arpa and gets a PTR record with the name you defined.

The problem I could think of is with any reputation system that checks reverse addresses and forward addresses and how the correlate, like for SMTP. They might get confused by this.

An idea to get around this would be some kind of generic address that is used as forward and reverse address and a "descriptive" address like:

(generic)
host1.network1.domain.tld -> IP1
host2.network1.domain.tld -> IP2

(descriptive)
awesomeproduct.domain.tld -> IP1,IP2
Christopher Perrin
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  • If each site on the server is primarily associated with one of the two IP addresses, and their respective PTR records point to the IP they're on, ie set at an account level rather than a server level (server is a DNS server as well as email). You'd consider there are not issue with having both IPs point to the same place? – Martin Nov 16 '18 at 15:18
  • The big question is why do you want to point two names at the same address. It is not as if the names are somehow short in supply. It is also good practice to have one name for one IP. – Christopher Perrin Nov 16 '18 at 15:19
  • My hosting provider screwed up and set the rDNS to my secondary IP rather than the primary IP and I'm unsure weather there is a need to demand they remove the secondary ip reverse DNS? Please note that Sven's edit on my Question is wrong and I will correct this now. 2 mins. – Martin Nov 16 '18 at 15:26
  • No -- NOT two names -- it's two IPs to the same name! – Martin Nov 16 '18 at 15:28
  • Yeah I meant one name to two addresses. I wouldn't do it especially if you host email on it. You might get bad reputation points for it. – Christopher Perrin Nov 16 '18 at 15:52
  • Thanks for the clarification, This solves my query! – Martin Nov 16 '18 at 16:06