I have two domains, example1.com and example2.com. I run nameservers ns1.example1.com and ns2.example1.com. Example2.com uses these nameservers. Example1.com uses my registrar's nameservers.
Under this scenario, I would expect not to need any GLUE records of my own, and I have not created any. However, using information in this post I have checked for the existence of GLUE records using the dig tool.
When I query h.gtld-servers.net (or any of the others) for example2.com's nameservers, I see ns1.example1.com and ns2.example1.com in the 'authority' section, but also their IP addresses in the 'additional' section.
;; QUESTION SECTION:
;example2.com. IN NS
;; AUTHORITY SECTION:
example2.com. 172800 IN NS ns1.example1.com.
example2.com. 172800 IN NS ns2.example1.com.
;; ADDITIONAL SECTION:
ns1.example1.com. 172800 IN A 192.0.2.1
ns2.example1.com. 172800 IN A 198.51.100.1
My understanding is that this means that there are GLUE records in existence for those nameservers, but my registrar insists that they do not exist. The only difference from the example given in the linked post is that I have two different domains, but I'm not sure if that's relevant.
Who is correct? My registrar, or the linked post? Do entries in the 'Additional section' always indicate the existence of GLUE records or can there be another reason?
Many thanks in advance.