I have registered a domain at CF. But can not find a link to create Child Name Servers like ns1. ns2.
In forum, it is said to create simply dns a records for them. But when doing so, other registrars does not accept these nameservers as a valid ones.
Child Name Server is not a term with a consistent and well established meaning, so it is a little unclear what exactly you are hoping to accomplish.
If you are simply wanting to operate your own authoritative nameservers on your own hosts using your own domain name for use with other domains, all you need to do is create A records using the IPs of the hosts that house your nameservers. Add AAAA records if you want them to be accessible over IPv6. Ensure that those hostnames are set to 
DNS Only.
If you want use Cloudflare’s nameservers and have them respond to names in your domain, you need the feature that Cloudflare calls custom nameservers. This will require glue records if they will serve as the authoritative servers for their own parent zone.
If you are seeking to delegate a child zone to nameservers outside of Cloudflare, that follows a different process.
Yes I want to create my own authoritative nameservers. But problem is, when simply creating A Dns record pointing to ip address , those name server is not accepted by other domains’ registrars. I tried many of them. They simple reject those nameserver as they are not valid. So I feel like I need to upgrade account to paid ones? Because there is not other menu for creating custom nameservers.
If you want, I can write ones that I created. They are not usable…
Have you asked your registrar why they are not accepting your nameservers? That’s where you probably should start. Unless your nameserver hostnames are set to 
proxied, this should be unrelated to anything at Cloudflare.
What have you named your nameservers?
Can you share the name of a zone that they are currently serving?
Ok they are (not proxied):
ns1.ns2ip.com
ns2.ns2ip.com
I tried three registrar and they generate:
In-Zone nameservers not added at the registry: ns1.ns2ip.com,ns2.ns2ip.com (Resellerclub)
or
Nameservers are not valid
So this can not be at their side. This is probably at cloudflare side. And I really do not understand how “must have action” this is no possible.
Can you ask them please if you have a paid account 
Mine is free…
What is domain name where are you trying to assign them as the nameservers?
Does it matter ? Any domain name does not accept them. You may try if you have a domain.
The records resolve…
dig +short ns1.ns2ip.com
178.210.181.103
dig +short ns2.ns2ip.com
178.210.181.103
As @epic.network says, that’s all Cloudflare has to do, and it’s doing it.
That resolver is refusing requests from clients (EDE 18) - well for me anyway so if its supposed to be globally available it isn’t.
dig ns2ip.com @ns1.ns2ip.com
; <<>> DiG 9.18.18-0ubuntu0.22.04.2-Ubuntu <<>> ns2ip.com @ns1.ns2ip.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 16607
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
; COOKIE: 74d2fdcb3e4d779d0100000065fdace8e3a01784f7e37338 (good)
; EDE: 18 (Prohibited)
;; QUESTION SECTION:
;ns2ip.com. IN A
;; Query time: 72 msec
;; SERVER: 178.210.181.103#53(ns1.ns2ip.com) (UDP)
;; WHEN: Fri Mar 22 16:08:08 UTC 2024
;; MSG SIZE rcvd: 72
So it does not work… No one is using child nameservers with Cf or what?
I do, pointing at a subdomain setup zone also on Cloudflare. It works as it should for both NS and DS.
Your problem is with the nameservers you are pointing at, not the Cloudflare configuration which is doing all it needs to do.
I do not think so. I also tried updating a domain at godaddy and got this:
We cannot save your changes that are not registered with this ad publisher. Verify that your listing is correct and check with the DNS provider this advertiser is registered with.
So resellerclub, godady and other two major domain registrar in Turkey does not accept them.
To recap, I registered a domain ns2ip.com at cloudflare and created two ns1 and ns2 A record. Am I missing something?
Yes, the DNS server at ns1.ns2ip.com (and ns2 which is on the same IP address, so the same resolver, not recommended) appear to not accept queries.
Mention a domain that should resolve at ns1.ns2ip.com for testing.
Just to be clear, Cloudflare does nothing for your DNS server other than return the IP addresses for them. It does that.
No man it is not about it. I deleted one record ns2.ns2ip.com still not accepting them.
As domain is registered at cloudflare. It it responsable for creating child nameserver to use on other domains. But there is not such option. All I can do is to create simple dns a record and they do not help.
Can you explain clearly what you are trying to do as none of what you have said makes sense?
If you want to create an external nameserver, you have to do that yourself. Cloudflare can merely point your subdomain at it using a DNS record as you have done (and seem to be doing).
Or are you trying to create a vanity nameserver as described here?
If so, do you have a Business or Enterprise plan? Such vanity nameservers can only be used for zones in your account.
Please read above. I explained everything.
I’ve dug deeper as your explanation isn’t clear, the internet isn’t clear on an answer either so I’ve dug deeper by using Godaddy with one of my test domains and pointing at yours, and various other nameservers of mine.
The message isn’t clear, so perhaps as the registrar themselves. This may be a glue issue, they may require the glue records for your domain to point at the nameservers you are creating. You could try to raise a ticket with Cloudflare to ask for this. It’s not something that would be done automatically.
Yes this is the issue I talk about. I tried creating ticket to CF but my account is free so they do not seem to help for free accounts…
That had crossed my mind as well, though it really should only be necessary when a nameserver needs to be authoritative for its parent zone.
You may not have created your request in the appropriate category. All plans can open account, billing, and registrar tickets. This would be a registrar support request, since your domain is registered with Cloudflare registrar, and the registrar is the party that needs to submit the glue records to the parent zone.
I thought the same as well, just may be overzealous checking. I tried Godaddy with my domain’s nameserver ns1.example.com (example.com registered on Cloudflare with ns1.example.com as an account vanity nameserver) and that was accepted (there is glue for that), but it refused to accept ns1.sub.example.com which are (zone) vanity nameservers for a subdomain setup (so the IPs for those won’t match the glue).
So I am not doing something missing ? I recreated ticket to cf and will see…
