Windows RDP firewall issues over VPN
Posted: Wed Mar 24, 2021 9:17 am
I have a site with local subnet 192.168.1.0/24, with:
Windows machine 192.168.1.3
Linux machine running openvpn server 192.168.1.4
I am connecting from a remote site with local subnet 192.168.2.0/24
The VPN network is 10.8.0.0/24
I have the router on the server network 192.168.1 set up with a static route
10.8.0.0 -> 192.168.1.4 (VPN server)
I found this was required in order to get responses to pings from the client network to machines on the server network.
If I turn the Windows firewall off on the Windows machine on the VPN server network then I can RDP from a machine on the VPN client network (e.g. 192.168.2.23) to the Windows machine on the VPN server network no problem.
If I turn the Windows firewall on then the RDP login box appears and accepts my password but then hangs with a black screen before eventually saying:
"The connection to the remote computer was lost, possibly due to network connectivity problems"
I can't find what the Windows firewall is blocking. I have allow Remote desktop for private and public networks enabled in the firewall settings.
I used wireshark to monitor the traffic with and without the firewall enabled and it looked like UDP from the Windows machine was being blocked, so I enabled allow all incoming and outgoing traffic to the 10.8.0 network in the firewall but that didn't help.
One thing I've noticed is that if I disable the firewall then enable it again, RDP connections work for about half an hour (i.e. disconnect/reconnect), but then at some point stop working until I toggle the firewall again.
With the firewall on I can ping the Windows machine from the client network and telnet to port 3389, it is only after establishing a RDP session that whatever traffic is required for the session gets blocked and kills the session.
Windows machine 192.168.1.3
Linux machine running openvpn server 192.168.1.4
I am connecting from a remote site with local subnet 192.168.2.0/24
The VPN network is 10.8.0.0/24
I have the router on the server network 192.168.1 set up with a static route
10.8.0.0 -> 192.168.1.4 (VPN server)
I found this was required in order to get responses to pings from the client network to machines on the server network.
If I turn the Windows firewall off on the Windows machine on the VPN server network then I can RDP from a machine on the VPN client network (e.g. 192.168.2.23) to the Windows machine on the VPN server network no problem.
If I turn the Windows firewall on then the RDP login box appears and accepts my password but then hangs with a black screen before eventually saying:
"The connection to the remote computer was lost, possibly due to network connectivity problems"
I can't find what the Windows firewall is blocking. I have allow Remote desktop for private and public networks enabled in the firewall settings.
I used wireshark to monitor the traffic with and without the firewall enabled and it looked like UDP from the Windows machine was being blocked, so I enabled allow all incoming and outgoing traffic to the 10.8.0 network in the firewall but that didn't help.
One thing I've noticed is that if I disable the firewall then enable it again, RDP connections work for about half an hour (i.e. disconnect/reconnect), but then at some point stop working until I toggle the firewall again.
With the firewall on I can ping the Windows machine from the client network and telnet to port 3389, it is only after establishing a RDP session that whatever traffic is required for the session gets blocked and kills the session.