whats the frequency of the letter 4 in:
q: ns records on nameserver for parked domain i have domain and i set ns records for this domain on registrator page.
for egz.: 
ns1.some.com
ns2.some.com

on these ns servers i have records a, mx.
if i need set ns records on ns1.some.com and ns2.some.com for any reason? is that does something?
what with soa record, where it should be placed?
thanks for answers.

a: yes, the name servers that are serving up the a, mx, etc records need to know that they are authoritative, so they must also have the ns records. you should configure one as a master and the other as a salve (if you have more than two the rest should all be slaves too).
the other answer has a lot of good information, but i dont think he ever actually answers your question.
if youre running bind, your master dns server should have an entry like this in named.conf:
acl mysecondaries {
        12.34.56.78;
};

zone example.com {
        type master;
        file master/example.com;
        allow-transfer { mysecondaries; };
};

on the slave server something like this:
zone example.com {
        type slave;
        file slave/example.com;
        masters { 1.2.3.4; };
};

the actual record (make this file only on the master) should look like this:
example.com.       in soa   ns1.example.com.  root.example.com. {
                                2012082401 ; serial
                                10800      ; refresh (3 hours)
                                3600       ; retry (1 hour)
                                604800     ; expire (1 week)
                                86400      ; minimum (1 day)
                                )

                ns      ns1
                ns      ns2

                mx      10 mail

ns1             a       1.2.3.4
ns2             a       12.34.56.78

mail            a       2.34.5.67

www             cname   park.domain.net
@               cname   park.domain.net

while im at it. there are free secondary/slave dns services so you dont need to operate two of your own. many personal and small websites are setup this way. i use afraid.net and buddyns.com myself. 
to add them, add the following to your named.conf on your master server:
acl afraid {
        174.37.196.55;
};

acl buddyns {
        173.244.206.26;
        174.136.99.149;
};

and change your allow-transfer directive for each zone in your named.conf on your master:
        allow-transfer { afraid;
                         buddyns;
                         mysecondaries; };

and add the relevant ns records to your zone files:
                ns      ns2.afraid.org.
                ns      b.ns.buddyns.com.
                ns      c.ns.buddyns.com.

there are various ways to get really fancy with these configurations (if the above seems really manual, it is; but that also makes it fairly easy). unless youre parking a ton of domains you really dont need to get into anything more complicated.

user
I found thirteen "4"s in the provided passage.
assistant