GCP/Google DNS: delegate a subdomain and set PTR records on VM instance

mr.szop

1/12/24, 4:03 PM

I am having a hard time figuring out what steps are needed to set a PTR record on a VM since I want to run a mailserver on it. My scenario looks like this:

(unfortunately because of planned migration) I have two GCP accounts and therefor two seperate GCP projects and therefor two GCP Cloud DNS
I own $domain.com and DNS is set up on first account
on second account: I created a new zone for mail.$domain.com (mail.$domain.com NS and SOA where created)
on first account: I delegated mail.$domain.com to second account by setting up DNS NS records for mail.$domain.com and enter provided nameservers of second account
on second account: I was able to create a A record for mail.$domain.com pointing to VM public IP and I can verify it resolves mail.$domain.com as expected to provided public IP

On second account: now I want to add the PTR record. My approach is to edit my running VM and edit network interface and adding "Public DNS PTR Record" - "Enable for IPv4" with value: mail.$domain.com. Unfortunately I am getting:

"Editing VM instance "mailcow-testing-tf" failed. Error: Invalid value for field 'resource.publicPtrDomainName': 'mail.$domain.com.'. Please verify ownership of the PTR domain at https://www.google.com/webmasters/verification/verification?domain=mail.$domain.com."

Following this link results in a dead end: "We are sorry, but you do not have access to Google Search Console. Please contact your Organization Administrator for access."

Question is: how to add a PTR record for my running VM in second account?

Cheers

204

0 + 2

reverse-dns

ptr-record

google-cloud-dns

mr.szop

1/13/24, 8:25 AM

Currently I am following the answer at https://serverfault.com/questions/779600/how-do-i-change-reverse-dns-on-google-cloud-compute answered Aug 3, 2017 at 21:56 by Jaques. It looks promissing

mr.szop

1/17/24, 3:01 PM

Unfortunately creating a dedicated PTR zone and pointing to public IP of VM doesn't work out. Using `dig -x "PUBLIC-IP"` I am still receiving: ``` PUBLIC-IP.in-addr.arpa. 120 IN PTR PUBLIC-IP.bc.googleusercontent.com. ``` which is not what I am expecting. Good thing is, my mailserver currently doesn't care so I have more time to figure out a solution.

Elon Musk

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EN: GCP/Google DNS: delegate a subdomain and set PTR records on VM instance

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