After reading here in the forums I did some changes:
I've changed nameservers in his control panel to
and now I'm waiting for him to confirm this change by clicking the link that his register sends him.
In godaddy DNS manager I've added new A (Host)
records ns1 and ns2 for a domain that I was using to setup ISPconfig i.e. myserver.com
Then I added new NS records ns1 and ns2.
default ns11.domaincontrol.com and ns12.domaincontrol.com can't be changed or deleted.
So, without adding A (Host)
record I can't ping ns1.myserver.com
Was a NS record necessary?
Do I still need to ask his register to add a glue record?
I would ask them to add ns1.myserver.com and ns2.myserver.com ?
Just to clarify:
All of my domains are registered with godaddy. My friend uses totally different register in different country and his only option is to enter ns1,ns2,ns3 etc.
This is how my DNS zone looks like now: