Private IP being used in public DNS

MissionControlFreak

6/2/24, 2:19 AM

I recently was working on a problem for a user at work. The basic problem was they had a bank scanner that connects directly to the bank but it wasnt working on our network.

The domain name was usb.rdmscanners.net when I tried to resolve this in our domain I wasn't able to but I tried externally and was met with 192.168.253.1 bear in mind this is using Oracle’s public DNS

The issue has been fixed on our end but why on earth would a private IP be allowed to be registered for public use?

Am I missing something here? I remembered reading about changes to the IP addressing schema somewhere but I cant remember where… thanks in advance

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networking

domain-name-system

Greg Askew

6/2/24, 2:27 AM

We aren't going to know the answer. Contact the domain owner. There's nothing to prevent a private IP address to be registered for a name in DNS.

HBruijn

6/2/24, 12:37 PM

https://serverfault.com/questions/4458/ has some interesting answers, comments and opinions as well.

Paul

6/4/24, 10:21 AM

Does this answer your question? [Private IP address in public DNS](https://serverfault.com/questions/4458/private-ip-address-in-public-dns)

Score:7

Server

HBruijn

6/2/24, 7:57 AM

why on earth would a private IP be allowed to be registered for public use?

There is absolutely no technical requirement, RFC or IETF Internet Standard or anything that requires that any public DNS record must only resolve to publicly accessible resources.

For example RFC 1537 even states:

Note that all domains that contain hosts should have a "localhost" A record in them.

So a localhost.example.com. IN A 127.0.0.1 record is fairly common to see and 127.0.0.1 is the epitome of private IP's.

It is perfectly valid to have public DNS records that resolve to restricted access resources, to resources that are powered off, offline and/or resources that reside in an internal network. That internal network may even use RFC 1918 private use IPv4 addresses.

For larger organisations, that have an internal DNS server, populating their public DNS zone with records for resources in their internal network is usually avoided and often considered "leaking information about the layout of the internal network" and a security risk.

But for a small business or a home office without an internal DNS server, setting up printer.office.example.com IN A 192.0.2.22 in their public DNS can make life easier for everybody in that office.

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