domains on the same host, same IP, same nameservers

[Mohamed Navas V]

Hi,
I have two subdomains a.abc.com and b.abc.com.

Can I have any options to accomadate two name servers in the same
physical servers ?

ie. ns1.a.abc.com and ns1.b.abc.com >> 10.10.10.1 and
    ns2.a.abc.com and ns2.b.abc.com >> 10.10.10.2

Or, Is it required separate name servers for different subdomains ?

thanks,
--Navas