Google Cloud Bring Your Own IP DNS/PTR Validation

Question

I'm trying to use a leased ip in my gcp VM. I've followed the instructions to create a PAP with my prefix (particularly this section), but I can't get the DNS validation step to work for me.

This is what I've tried:

• Pick an IP from the prefix range for DNS validation. eg. 12.34.56.78
• Google will generate a secret name, eg. qwerty
• I also have a registered domain with the project, though not sure if I should use it, eg. domain.com

I tried using the cloud console for the project to run the following command

dig +noall +answer -x 12.34.56.78 78.56.34.12.in-addr.arpa. 21599 IN PTR qwerty.domain.com

I also tried omitting 'domain.com' from above.

Separately I also tried to use Google DNS to create a managed zone by doing the following:

1. 'Create Zone'

   1.a Add any zone name

   1.b DNS name is: 78.56.34.12.in-addr.arpa. (I also tried 56.34.12.in-addr.arpa.)

2. 'Add Record' to zone

   2.a Leave DNS name as is from 1.b above (don't fill in anything)

   2.b Select PTR

   2.c For Canonical name add qwerty.domain.com (also tried just qwerty)

Validation fails for all cases.

I also tried following this post but to no avail.