In the installer we do configure some things for DHCP
It tries to configure a subnet based on an interface. This is because ISC DHCPd will refuse to start up if no subnets have been defined. If you’re managing it by yourself via the ENC, you need to take care of this yourself. The module’s README has some information but that’s mostly focused at writing a profile module. Sadly we also haven’t spent much time at documenting the options.
The short version is that you should use the pools option to define a subnet. The options are name => dhcp::pool. Looking at it, subnet would have been a better name.
Patches to puppet-dhcp are highly welcome, in particular documentation.