Resolving local hostnames (via DNS) from DHCP assigned IP's / Device Inventory

[Algilstrap]

Hi everyone, I have searched forums and the web and cannot seem to find the solution. On a Fortigate 60e does it have the ability to run it's own DNS server and resolve internal hostnames to IP that are assigned by the internal DHCP? If I use the "system DNS servers" on the internal interface I can resolve external (internet) hostnames, but not the internal (interface based) hostnames. If I assign the "interface" gateway as the DNS server I can resolve internal but not external hostnames... Am I missing something simple? I don't want to have to maintain a local DNS database as it needs to be dynamic and automatic as new devices join the private network they need to be resolved immediately. Any suggestions as to how to make this work? Many thanks!