"A" records of a particular name can co-exist with all rrtypes except CNAME (as CNAME's cannot co-exist with any other RRType).
In most cases, the "A" record will be the answer given to an "A" query.
However, there are some interactions to keep in mind.
| QType | Config | Response |
| A | NS and A of same label | NS |
| A | Wildcard NS + CNAME whose label is subdomain is within scope of NS wildcard | CNAME |
| A | NS + CNAME whose label is subdomain of NS | NS |
| A | ApexAlias + A, same label | A |
| A | ApexAlias + CNAME, same label | CNAME |
| A | A and Wildcard of Same Label | A |
| A | CNAME + Any RRType other than ApexAlias | Unsupported Configuration |
Scenario 1: Conflicting NS Record.
Zone: domain.com.
sub.domain.com. IN A 10.1.1.1
sub.domain.com. IN NS delegated.name.server.
sub.domain.com. IN NS delegated2.name.server.
Here, the NS record will be returned. NS will be returned, and our "A" record will be ignored.
Scenario 2: Conflicting Wildcard NS Record
Zone: domain.com.
sub.wild.domain.com. IN CNAME other-domain.com.
*.wild.domain.com. IN NS delegated.name.server.
*wild.domain.com. IN NS delegated2.name.server.
A query for sub.wild.domain.com is answered by the specific CNAME. Specific CNAME will win over wildcard NS.
A query for test.wild.domain.com (which has no configured CNAME) is answered by the NS.
Scenario 3: Multidotted Labels
Scenario 4: Conflicting Apex Alias Record
Zone: domain.com.
domain.com. IN A 10.1.1.1
domain.com. IN RNAME www.domain2.com.
Here, the "A" record will be returned. What's noteworthy about Apex Alias is that it can co-exist with both "A" records and CNAME's but will always be blocked by them. In other words, the Apex Alias will only ever be response if there is no configured "A" record or CNAME of the same name.
Scenario 5: Conflicting Wildcard Record
Zone: domain.com.
sub.domain.com. IN A 10.1.1.1
*.domain.com. IN A 10.5.5.5
Here the specific record will take priority over the wildcard record. If the specific record is deleted, the wildcard would answer for it.
Things I need to consider
Some might wonder how NS records pointing to us don't prevent "A" records of the same from resolving. It's because it's saying we're authoritative so we still ultimately return the "A". But I need to think about how to show/say that.