I'm in the process of setting up a VM environment for a MS certification exam (70-462). Following the training kit's instructions, I've set up a domain controller (DC) and two members (SQL-A, SQL-B) thus far. I can't figure out why I can't join the domain. DC IPv4 Address . . . : 10.10.10.10(Preferred) Subnet Mask. . . . : 255.0.0.0 DNS Servers. . . . : ::1 127.0.0.1 SQL-A IPv4 Address . . . : 10.10.10.20(Preferred) Subnet Mask. . . . : 255.0.0.0 DNS Servers. . . . : 10.10.10.10 SQL-B IPv4 Address . . . : 10.10.10.30(Preferred) Subnet Mask. . . . : 255.0.0.0 DNS Servers. . . . : 10.10.10.10 I've read how to do networking between virtual machines in virtualbox and the documentation. After trying various network adapter configurations, I can't get them to communicate in order to have the two members join the domain. When I ping from .30 to .10, I get: ping 10.10.10.10 Pinging 10.10.10.10 with 32 bytes of data: Reply from 10.10.10.20: Destination host unreachable. Reply from 10.10.10.20: Destination host unreachable. Reply from 10.10.10.20: Destination host unreachable. Reply from 10.10.10.20: Destination host unreachable. Trying to join the domain: netdom join SQL-A /domain:contso.com The specified domain either does not exist or could not be contacted. The command failed to complete successfully. Within VirtualBox, I've tried the following combinations for network adapter: Attached to - Promiscuous Mode ------------------------------- NAT Bridged Adapter - Deny Bridged Adapter - Allow VMs Bridged Adapter - Allow All Internal Network - Deny Internal Network - Allow VMs Internal Network - Allow All Host-only Adapter - Deny Host-only Adapter - Allow VMs Host-only Adapter - Allow All Edit ipconfig /all of DC ipconfig /all of SQL-A