Add A, AAAA, and CNAME record for google app engine project in google cloud platform

Question

I am adding a new google app engine project and trying to map it to a subdomain.

I have already created a CNAME which maps newmachine.mycompany.com to newproject.appsport.com, and I am able to use it in 'App Engine' -> 'Settings' ->'Custom domains'.

But once the mapping is finsihed, the same screen shows the following messages:

Configure resource records on your domain registrar
Have your domain registrar add the following resource records for mycompany.com:
Type    Data    Alias
A   215.234.32.21   
A   215.234.34.21   
A   215.234.36.21   
A   215.234.38.21   
AAAA    1997:2340:4801:32::15   
AAAA    1997:2340:4801:34::15   
AAAA    1997:2340:4801:36::15   
AAAA    1997:2340:4801:38::15   
CNAME   ghs.googlehosted.com    newmachine

I haven't seen this message before. As a matter of face, no such A and AAAA were created for other existing GAE projects.

My questions are:

1. What is the implication of NOT adding these records to my DNS server?

2. What purpose do they serve? Is it simply to provide a reverse IP lookup?

Answer 1

The list seems to be incomplete and confusing, but I guess it means:

@           IN A     215.234.32.21   
@           IN A     215.234.34.21   
@           IN A     215.234.36.21   
@           IN A     215.234.38.21   
@           IN AAAA  1997:2340:4801:32::15   
@           IN AAAA  1997:2340:4801:34::15   
@           IN AAAA  1997:2340:4801:36::15   
@           IN AAAA  1997:2340:4801:38::15   
newmachine  IN CNAME ghs.googlehosted.com.

That's because @ IN CNAME wouldn't make any sense, as an alias defined by CNAME should not have any other type records, including mentioned A / AAAA, but also MX breaking email and NS & SOA breaking the DNS itself; see the canonical question about CNAMEs at the apices of zones.

Now, because you already have newmacine CNAME and don't want to move whole example.com to Google App Engine, there shouldn't be any reasonable purpose for the other records.