Multiple nameservers, different servers
I've decided to diversify on reseller accounts, so I can offer different types of hosting on different server setups. My question is how do I go about setting up my nameservers for my domain to their respective IP addresses. So for example:ns1.mydomain.com -> IP Address 1 on Server 1
ns2.mydomain.com -> IP Address 2 on Server 1
ns3.mydomain.com -> IP Address 1 on Server 2
ns4.mydomain.com -> IP Address 2 on Server 2
etc.
My domain is registered through Enom, and I've added all my nameservers to their respective IP addresses using Enom's "register DNS" function. I've got my domain pointing to my ns1/ns2 nameservers. My ns1/ns2 nameservers work as when I ping them they return the correct IP address. However, my other nameservers (i.e., ns3/ns4) don't work as I get nothing back.
I'm a bit lost, so any help would be greatly appreciated.

Malikay.