What happens if a domain name is sent to two DNS with different settings?

Question

Domain Name System

Hello.
There is a blabla.com domain
By default, when we bought it, it was directed to dns.ya.ru and led to some left ip
Later we decided to redirect it to our DNS ns.bla.com, but the old ones were not deleted.
And as a result, blabla.com has 2 DNS bindings.
What can be kabzdets?

Answer 1

several options
1. If you specified a new NS server, then the old one will give its A record if you explicitly specify the NS server from which you will request the Address. for example host -a site.ru ns1.site.ru
2. Two ns servers, in this case you will receive information from one of them, and from the second in the absence of the first.
3. You have specified two A records, in which case they will be issued in 50/50 percent case

Answer 2

NS are set to primary and secondary. If you changed the primary, but data from it is not forwarded to the rest, then if the primary NS fails, the addressing will lead anywhere to the secondary NS.
In general, there should be several specified NS, at least 2.

Answer 3

1. Everything is correct, there should be 2 of them
2. All records inside both NS must match (then no matter what dns answers, it will be correct everywhere)
3. Set up synchronization, or edit the ns zone manually if no edits are planned

Answer 4

Eee. And if I now create this domain on my dns server, will it be the third binding?
Here is what is indicated in whois - this is the dns of the domain server.
If both old and new dns servers are indicated there, then we will get a lottery)