IP address showing default, but domain name not accessible

Hi guys, I had 4 IP IPV4 on servermania, I set the first IP as the shared default, and the 2 remaining as NS1 & NS2,
I had my 3 domain registered at 1and1, they do not allow same IP's on IPV4 thats why i use two different IP...

My question is, after setting all that needed to be set up... and try my main site it not accessible via domain name but i can access it using IP address.. But NS1.mydomain.com and NS2.mydomain.com is accessible by their names... Any suggestion to fix this issue?

Anyone? Your Help is mostly appreciated...

Thanks in Advance....