[Samba] KVM install failure

[Eric Smith]

Just as a means of testing and toying with some AD integrations I’ve been trying to create a working Samba4 AD DC on a KVM VPS. I am using Ubuntu 12.04.3 64-bit LTS server as the OS, scratch install from .ISO. I run through exactly the same steps as I do for creating a local Samba4 DC that works like a charm, but when I try to join a Windows 7 client to my KVM Samba4 AD DC I get a credential request and then after some time an error on the client that says: 
“The following error occurred attempting to join the domain “domain.com”
The network path was not found”

The client’s sole DNS i server is set to the AD DC either case. So on the internal AD DC it’s manually set to the internal IP for the Samba4 server (which works) and for the KVM VPS it’s set to that server’s IP.

I have run through the DNS tests as described in the samba.org AD DC how-to wiki article and they come back as expected. I am using to following as my DNS setup and have my authoritative external DNS servers pointing to the DC’s subdomain as well:

Server Hostname:        DC3
DNS Domain Name:  add.domain.com
NT4 Domain Name:        domain
IP Address:             my external IP
Server Role:            DC

Any clues as to which logs/what I can look at to get a better handle on why this is failing? It’s not an ACL issue, etc, but I’m guessing something DNS related. The funny thing is the exact same setup on my internal network works like a charm…
Any thoughts would be greatly appreciated.

thanks!