ping my internal domain

Ping Domain will ping list of IPs in Domain NS record (mostly all DC's) bacuase to provide a failover, you can see the list of IP's by nslookup

Nslookup DOMAIN.LOCAL

No, the NS records have nothing to do with it.

There are host (A) records for domain.local (or whatever your domain name is), that point to the IPs of all of your domain controllers - one record for each IP.  These A records are like any other A record.  When a DNS query is performed for a name and there are multiple records, every result is returned, but the order of the results can vary depending on settings in the DNS server.  By default, round-robin is turned on meaning the results will be reordered each time they are queried.  Subnet prioritization/netmask ordering can also come into play on the server which can affect the order of the results if the client IP is in a matching subnet.  The client performing the query then generally picks the first in the returned list.  Other factors on the client can come into play such as caching and subnet prioritization settings.  Feel free to read up on round-robin DNS and subnet prioritization/netmask ordering if you really want to get in depth.

This is all separate from any sites you may have configured in AD, as ping is not site-aware.

ok thanks
Do you have some good links for this round-robin DNS ?

ok have found some nice videos.

But I have one more thing, when send the command nslookup domain.local
I get a list of oall my DCs.
But two IPs are from the CLUSTER network . How can it be ?

Here's some articles.
http://blogs.msmvps.com/acefekay/2010/05/29/dns-and-subnet-priortization-amp-dns-round-robin/
http://blogs.technet.com/b/networking/archive/2009/04/17/dns-round-robin-and-destination-ip-address-selection.aspx
https://technet.microsoft.com/en-us/library/cc787373(v=ws.10).aspx

You can read the entire "How DNS Works" if you want to cover a lot.
https://technet.microsoft.com/en-us/library/dd197446(v=ws.10).aspx

I don't know what your CLUSTER network is.  The IPs you mention, are they on your DCs?

no it is the just the cluster network for the windows cluster with subnet 255.255.255.252

It sounds like those records aren't needed, but there's no way I could say for certain without really knowing your network (i.e examing it personally).  All the DOMAIN.LOCAL A records should resolve to your DCs, and these records should be automatically recreated if they don't exist whenever the Netlogon service is restarted on the DC and periodically (time period depends on Server OS version).

Ok I have checked in my DNS-Manager and my domain.local DomainDnsZones

Here are all Cluster entries, also 10.250.1.1 and 10.250.1.2.
It is written same as parent folder.

But how it comes, that the cluster IPs in this folder ?
What kind of IPs are needed in the folder DomainDnsZones ?

can I ask you something else ?

If it's related to this question, but it would probably be more appropriate to open a new question.

ok I open up a new one.