I need to set external name servers for my subdomain. Do I also need to set A record for that subdomain? Why after adding the NS records they still did not reflect at Nameserver Check tool? How long does it take for the records to be cached by another name servers?
If you're setting NS records to point a sub-domain to an external nameserver host, you'll set up the DNS records in the external nameserver host.
Let's say you delegate sub-domain1.yourdomain.com to ns1.externalns.com. You must configure zone records in ns1.externalns.com - such as an A, MX, CNAME, TXT, etc... for that specific sub-domain. If you don't configure any records, you won't receive a response - EVEN if you have a sub-domain1.yourdomain.com record within our Zoneedit Zone - you won't get a response because you're delegating it to external nameservers.
Query the SOA for the sub-domain and see which nameservers report back as authoritative.
Provide us with the domain/sub-domain to do some queries/checks.
First, I'd like to remark, that my nickname is spelled in all lowercase (not capitalized).
Second, excuse me, but I was supposing that my question didn't include discussion of external nameserver parameters. No need to say that external nameserver settings are unrelated to ZE. My question is just about pointing my subdomain (of a domain operated by ZE) to external nameserver.
I use this site to verify DNS records. Also, do a successfully added NS records for subdomain (pointing to an external nameserver) must appear in Nameserver Check tool report? If I edit (for example, add) NS records for subdomain, ZE control panel says that maximum propagate interval is 5 minutes. But I doubt it. Could it be longer in majority of cases? If yes, what is an interval that's closer to, say, ¾ of cases?
Sending you domain and subdomain in conversation.
It depends on how you're looking up the records. Depending on a few factors. Is the sub-domain a new record, or was it an existing record? If the record previously existed, did you query it, and what is the TTL on your zone/record? It's not a simple answer without knowing specific details of any background influence.
When you perform the trace (from the conversation), what actually you're tracing? If IP address, then it has no sense since external nameserver can't take control of the subdomain (IT is the problem, indeed) for adding any record, including A.
Of course, the subdomain is a new record! What answers I should give also to diagnose the problem? Ask all the questions for it. And describe, please, a diagnostic scenario(s) in detail for this case. Thanks.
The two A and one CNAME records we're currently witness for the subdomain could be a remnants of my prior configuration I made several hours ago (then reverted) as an experiment, by adding A record for the subdomain HERE (in the ZE configuration). Could it be?
The default TTL in your zone is 5 minutes, so any changes you made would have expired in any DNS Resolver cache after 5 minutes. So, no, the CNAME or A Records you added (if they were added after the NS record configuration) would have no routing effect since you're delegating the sub-domain to an external set of nameservers.
Answer, please, which of the both nameservers (ZE and the external) must/can (answer separately) propagate NS records pointing to external nameserver? Or this propagation (to the global servers) even not needed?
When using NS records in the Zoneedit zone, you do not need to delegate the external nameservers to the WHOIS (global/registry). We need to be the authoritative servers, so the requests come to us first and are then redirected via the NS records within the Zoneedit zone file.