Set up nameserver with subdomain at different locations

Hi, I am getting issues of setting up subdomain for vps at different location. The details are:

A VPS server in US (ip 1.1.1.1 -example), I set up with the main domain mydomain.td and First Nameserver ns1.mydomain.td ip 1.1.1.1 (example) and Second Nameserver ns2.mydomain.td ip 1.1.1.1 (example)

B VPS server in Singapore (ip 2.2.2.2 -example), I set up the subdomain sg.mydomain.td and ip point to ip 2.2.2.2 . I create nameserver in Singapore with this subdomain sg.mydomain.td and First Nameserver ns1.sg.mydomain.td ip 2.2.2.2 and Second Nameserver ns2.sg.mydomain.td ip 2.2.2.2 (example)

Then, I get issues when I enter ns1.sg.mydomain.td and ns2.sg.mydomain.td on the panel of domain suppliers namecheap and others, they do not accept these dns ns1.sg.mydomain.td and ns2.sg.mydomain.td.

How can I configure dns records (or what else) on server in US and server in Singapore to make them work? Thank you soooo much!

In the server one which have main domain use only that’s name servers and after that check the add records in the server b and update IP for the subdomain there

Could you tell clearer please?
Which records or what else to do on server 2 (server with subdomain in singapore)?
When I only use main domain and subdomain on server 1 in US, so ns1.sg.mydomain.td and ns1.sg.mydomain.td cannot be pinged.

i think you are not talking as cyberpanel user

well… global issue

why domain provider reject ns1…sg.mydomain.td ?
thats because this:

mydomain.td IN NS ns1.mydomain.td
mydomain.td IN NS ns2.mydomain.td
with
private NS Configuration :
ns1 IN A 1.1.1.1
ns2 IN A 1.1.1.1

solution:
at server A you edit the zone…
add this
sg.mydomain.td IN A 2.2.2.2
ns1.sg.mydomain.td IN A 2.2,2,2
ns2.sg.mydomain.td IN A 2.2.2.2

—or----
use registrar dns not private dns

(edited)

Thank you for your reply so much!
I am using two servers with cyber panel.
And, I did as your solution but they do not work.

— and you said: or, use registrar dns not private dns
I do not know how to check dns not private or not, but I am using my own domain and subdomain.

---- it works on another way, but I do not like this way.
add dns nameserver with the own domain dns, (register domain suppliers allow):
Example: Domain domaintest.td point to
ns1.domaintest.td ip 2.2.2.2
ns2.domaintest.td ip 2.2.2.2 (ip of singapore server)
It works.
Although I try to config Default Namservers for ns1.sg.mydomain.td and ns2.sg.mydomain.td for all domains on the server B in Singapore, the domain suppliers tell going wrong some ways (when using ns1.sg.mydomain.td and ns2.sg.mydomain.td)
Could you please tell what the issue is? Thank you!

actually what you want to do…

i little lost here

Thank you,MyIDKaTePe for following the topic!
But, the solution does not work for the server in Singapore with subdomain.
Thank you again!

do you mind to PM me the domain name and sent me more info what is exactly you want as a final goal ?
maybe i can help