Make sure you use Host-Only network adapters for both DC and guest machines, Host-Only network adapter provides DHCP and DNS service.
If you’re using internal network, either configure your own DHCP or set static IP addresses.
Configure the DC also as a DNS server, so that it can resolve domain name to IP address when query. If not, register the DC to the DNS server.
If the DC is also a DNS server, set its IP address to the network adapter of member machines, so those machines can find the DC to join domain.
Make sure ports are allowed in firewall settings.