When configuring test.example.com with both an A record and NS record, we create a fundamental DNS resolution conflict. The scenario presents two competing configurations:

<!-- Original zone file at example.com -->
test.example.com.    IN    A    1.1.1.1
test.example.com.    IN    NS   ns1.anotherdnshost.com

The actual resolution depends on several factors in the DNS lookup chain:

• Resolver caching behavior
• TTL values of the records
• DNS server implementation specifics

Here's what happens during resolution:

dig test.example.com +trace
; <<>> DiG 9.16.1 <<>> test.example.com +trace
;; global options: +cmd
.                       3600    IN      NS      a.root-servers.net.
;; Received 525 bytes from 8.8.8.8#53(8.8.8.8) in 4 ms

com.                    172800  IN      NS      a.gtld-servers.net.
;; Received 1172 bytes from 198.41.0.4#53(a.root-servers.net) in 28 ms

example.com.            172800  IN      NS      ns1.example.com.
;; Received 840 bytes from 192.5.6.30#53(a.gtld-servers.net) in 32 ms

test.example.com.       3600    IN      A       1.1.1.1
test.example.com.       3600    IN      NS      ns1.anotherdnshost.com.
;; Received 120 bytes from 203.0.113.1#53(ns1.example.com) in 16 ms

Most DNS implementations will prioritize the NS record over the A record when both exist for the same name:

1. The resolver first sees the NS record delegation
2. It then queries the authoritative servers listed in the NS record
3. The final A record (2.2.2.2) from the delegated zone is returned

To avoid unpredictable behavior:

<!-- Recommended configuration -->
; Option 1: Full delegation
test.example.com.    IN    NS    ns1.anotherdnshost.com.
test.example.com.    IN    NS    ns2.anotherdnshost.com.

; Option 2: Non-delegated with glue records
test.example.com.    IN    A     1.1.1.1
www.test.example.com. IN    A     1.1.1.1

To verify your specific configuration:

# Clear local DNS cache
sudo dscacheutil -flushcache # macOS
sudo systemd-resolve --flush-caches # Linux

# Perform clean query
dig @8.8.8.8 test.example.com +norecurse
dig test.example.com +trace

In DNS configurations, having both A and NS records for the same subdomain creates an ambiguous situation that DNS resolvers must handle. Let's analyze the technical behavior when test.example.com has:

; Zone file for example.com
test.example.com.    IN A     1.1.1.1
test.example.com.    IN NS    ns1.anotherdnshost.com.

Meanwhile, at anotherdnshost.com:

; Zone file for delegated test.example.com
@    IN A    2.2.2.2

The resolution depends on the resolver's implementation, but generally follows these steps:

1. Recursive resolver checks cache for test.example.com
2. If not cached, starts from root servers down to example.com authoritative servers
3. Finds both A and NS records at the parent zone

Different DNS servers handle this differently:

Let's examine real-world behavior using the dig tool:

dig test.example.com A +trace
; Expected output shows delegation chain
; Final answer typically comes from the NS-delegated servers

In standard DNS implementations:

• The NS record takes precedence over the A record
• Resolution continues with the delegated nameservers
• The A record at the parent zone is effectively ignored

To avoid ambiguity:

; Recommended zone file
; Either delegate completely:
test.example.com.    IN NS    ns1.anotherdnshost.com.
test.example.com.    IN NS    ns2.anotherdnshost.com.

; Or handle locally:
test.example.com.    IN A     1.1.1.1
www.test.example.com. IN A    1.1.1.1