Can't get AD and SMB to work from Azure to On-prem server

Question

Hi,

I'm working on a newly created Azure environment with very little networking set up. Our setups are as follows:

Azure:

• Working S2S VPN
• Route table pointing to the on-prem subnet
• A VM for testing with an NSG allowing all traffic both inbound and outbound

On-Prem:

• Necessary firewall rules (Palo Alto) to allow AD, SMB, RDP, and ping
• A domain controller and a file server

I've just managed to get RDP and ping to work, but there was a strange issue (I'm new to all this). The issue was related to how RDP traffic from Azure was detected under the "cotp" app ID instead of "ms-rdp," which I normally see in the logs.

Right now, I'm at a loss trying to get the Azure VM to talk to the on-prem Domain Controller and the file server. The only traffic I'm seeing on the firewall for SMB shows up under the "quic" app ID. I've allowed this traffic to go through, but I still can't access the file server over SMB. No other traffic is showing in the logs except for "quic," which has been allowed. The other weird issue is that I can't see any AD-related traffic at all. I was hoping to see something getting blocked at the very least, but I see absolutely nothing. I've also configured the Azure VM's DNS to point to the on-prem DC, and that didn't help either.

Can anyone please shed some light on whether something is missing? I just want to be able to connect to the on-prem server from Azure via SMB and join the server to the domain.

Many thanks,

J