In most situations you are going to have VPN or private network to allow DC to DC traffic to work across the internet, in fact you would need either a VPN or private link as NAT would not allow it to work period. In the rare cases you would need to allow the communication between non-natting internal firewalls on different networks. This is what you’d need to allow

Required Ports

 TCP/UDP 389
 TCP 636
 TCP 3268
 TCP 3269
 TCP/UDP 445
 TCP 25
 TCP/UDP 135
 TCP/UDP 49152 - 65535
 TCP 5722
 TCP/UDP 464
 TCP 9389
 TCP 139
 UDP 123
 UDP 137
 UDP 138

I know there is a lot of ports required. Especially the large range of ephemeral ports. This is because Windows uses a port mapper to map these ephemeral ports. You can download the handy port query tool from Microsoft for finding out which ports are in use:

PortQryUI – GUI – Version

or google it of course. Thanks to Ace Fekay for his post:


Domain Controller to Domain Controller through Non-NATing Firewall
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