Google Cloud DNS – add a CNAME to another domain

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I can't add a CNAME to another domain – why and how can I fix?

My zone name is myapp.com. To add automated email security re spam, SendGrid (provider) wants me to add 3 CNAME records of the format:

 - mail.myapp.com             a123.b456.sendgrid.net
 - s1._domainkey.myapp.com    s1.domainkey.a123.b456.sendgrid.net
 - s2._domainkey.myapp.com    s2.domainkey.a123.b456.sendgrid.net

I can't do this. There is no error, the create button just does not work. I can however create CNAME records to my own domain.

Am I breaking the DNS rules or is this a Google Cloud limitation??

EDIT: Screen shot added.

Redacted parts are all myapp.com except the last two which is the SendGrid code. "Respond" is my subdomain. The existing CNAME is just a test to show I can add CNAMEs.

Best Answer

Ahh, I see the problem.

MX and CNAME records of the same name cannot exist within the same zone. You'll need to rename one of them.

Related Solutions

DNS: Google Apps Mail MX record issue caused by CNAME from EC2

You cannot use a CNAME on the bare domain name (what you are calling the "root domain"). This is a known limitation of ELB (elastic load balancer) on EC2.

The solution, released recently by Amazon, is to use Amazon Route53 to host your DNS. This integrates with ELB to handle bare domains without CNAME. Your MX records can still be pointed at Google with Route53.

Domain – How to redirect domain A to domain B using A-Records and CNAME records only

So you are not looking at redirection as such (as that happens at the app level, i.e. on Apache/Nginx/wherever) but rather on the DNS resolution. The host on which DomainA is hosted will or should never be hit, based on your description as you want the DNS requests to be resolved to the IPs of DomainB. Unless I'm missing something in your request?

As Shane pointed out DNS is not capable of HTTP redirection - that's an application/webserver duty. You could make DomainA and DomainB resolve to the same IP on DNS and all would work. But if you're looking to do this on per URL/per-path way then this is not possible - DNS is not capable of that - it's a simple DNS->IP service, what's happening with the actual URL is the webserver's task.

After the comment below, what I'd do is to refer all DNS records for DomainA to the same IP(s) as DomainB is pointed to - this way you will get HTTP request hitting hostB and then it's just a simple matter of:

creating a particular Apache Name Baseed Virtual host - which will be serving files from its own DocumentRoot
creating permanent redirect on Apache like this:

This will rewrite anything coming to DomainB to DomainA which can be hosted on the same server or somewhere else. I appreciate that the second option is probably an overhead and not necessary if you can/are allowed to create Name Based Virtual hosts on apache.

<VirtualHost *:80>
  ServerName DomainB
  Redirect permanent / http://DomainA/
</VirtualHost>

I'd go with 1. - point all DNS records of DomainA to the same IP(s) as DomainB is pointing and create particular Name Based VirtualHosts on Apache.

Best Answer

Related Solutions

DNS: Google Apps Mail MX record issue caused by CNAME from EC2

Domain – How to redirect domain A to domain B using A-Records and CNAME records only

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