DHCP service on WS2008R2 guest

[Mnstrspeed]

I'm trying to setup a DHCP server on my Windows Server 2008 R2 guest to provice DHCP services to other (Windows 7) guests in the internal network (for learning purposes, I'm aware of the built-in VirtualBox DHCP server). Everything seems fine (the DHCP server is authorized by AD, I have an active scope setup, the service is running and I'm not getting any error messages in the logs), but for some reason the clients can't seem to be able to contact the DHCP server. They're also unable to ping the server unless I assign a static IP on the clients (the server already has one for the DHCP service).

When running an "ipconfig /renew", it says it was "unable to contact" the DHCP server and the request has timed out. Running this command increases the number of discovers in the statistics for the DHCP service by about 18, yet the number of requests stays at 0.

Something (VirtualBox?) seems to be blocking the connection; firewall is disabled for both the server and the clients, and VirtualBox isn't running any internal DHCP servers (I checked using "VBoxManage list dhcpservers"). I've been stuck on this issue for quite a while, so I appreciate any help.

Thanks in advance.

(I'm running VirtualBox 4.0.6 on a Windows 7 Ultimate 64-bit host)

[Sasquatch]

I just configured a Windows 2003 VM (non-AD) with DHCP and set an XP VM to be the client on Internal Networking and the client got an IP in an instant. Now the systems are different, but the technique is the same: it proofs that intnet is not the problem here for DHCP.
So, you have to check the system for firewall settings and such to figure out why it doesn't work for you. I know that 2008 R2 has a firewall enabled by default and it might be conflicting with your DHCP requests coming in.