Microsoft Tunnel is connected, but no traffic goes trough

[train-IT]

When creating a Microsoft Tunnel Server as a VM in Azure using the Deployment Guide (Download Microsoft Tunnel Deployment Guide v2 from Official Microsoft Download Center) my Android and iOS Devices are connecting correctly, but no traffic is flowing back through the tunnel. The Linux VM itself has local and Internet connectivity. All self checks work, even the internal network check, all checkmarks are green.

So there must be some routing magic missing between the containerized VPN Server and the VM - I feel that the Azure Networking does not now how to backroute the pakets into the Container VPN Network. 

Has anybody ever built a working demo? I did it multiple times, always the same problem...

Waiting for your suggestions, Regards

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[#2]

@train-IT 

Can you let us know some more detail. From Azure (Tunnel Gateway Server) what do you use to get the traffic from Azure to on-prem (site2site, ExpressRoute). What Linux OS do you use? 

Did you check the logs from the Gateway to see if there are errors present? See here: microsoft-tunnel-monitor

On the resource server do you see any traffic coming in, for example from the logs?

[#3]

It's a totally simple setup for training. Just 2 VMs in Azure, one is the Tunnel Gateway, the other vm is a WS2022 Domain Controller with IIS installed for the Tunnel health check. Both VMs are in the same VNet/Subnet. DC is the DNS Server for the Subnet and DNS in the Tunnel policy. On Android Devices even the split tunnels works, so addresses outside the range will not be routed through the Tunnel. Addresses inside the range run into the "dead end". So for example when I try to navigate to http://10.0.0.4 in the mobile's browser nothing happens. Even if this address is the successfully logged health check address from the Tunnel's health check. In the logs on DC's IIS a see the Tunnel VM reaching IIS beacuse of its health check, but not anything coming from inside Tunnels Containers. So some routing information must be missing here. Linux is Red Hat 8.4 Gen2.