You need at least 2 Domain name servers for a domain to operate. That's just how it is. (rules) Officially each Domain name server should be in a different subnet. But it's not required by most.
Reasons for this are mostly, redundancy.
So, to come back to your question:
there are a few scenario's...
- if you have more than one public IP assigned to your connection, you could give your machine both ip's, and than setup the nameserver (both master/slave in one), and make sure domain.com changes the DNS server to your IP's.
- If you have only one, you could become the master of the domain, and domain.com the slave (i don't think you can set that up through a control panel, and you should ask them to set it up for you (their slave part))
- If you have only one, you could keep the DNS at domain.com and change the dns records within the zone, pointing them to your ip, instead of theirs. e.g.
<yourdomain.tld>. IN A <yourip>
<subdom> IN A <yourip>
<yourdomain.tld>. IN MX 10 subdom
etc etc etc
hope this helped you answer your question.
Oh and one thing:
make sure you are allowed to host services on your internet connection. (not every provider allows it.)
And make sure the ports you need are open to the outside world (some providers block e.g. port 80, 21 and 25 (http, ftp connection and smtp respectively))