[Domain Mapping] IP for domain

Hi guys, I'm trying to use the domain mapping plugin but im now the dedicated IP for my multisite domain is not pointing or redirecting to the main domain, can I be advised how to make my ip to show my main domain please instead of this

I have root/ssh access to the server but I'm not sure which command line to use to make this possible. I must also mention that the server already have host name but I would like to believe that that is different from what I'm looking for as I use the the host name for accessing whm/cpanel/webmail etc. I stand to be corrected.