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I have 2 small networks joined using OpenVpn (routed configuration), lets call them A and B.

on A, I have a test web server (IIS, Windows 2008R2 or Windows 2012 depending on test machine), lets call it webA :

  1. I can connect to it from network A (both RDP and HTTP)
  2. I cannot connect via RDP to webA from network B
  3. I can ping webA from network B
  4. I cannot connect to webA using : telnet webA 3389 Here things starts getting real strange :
  5. I can connect to webA using HTTP
  6. AFTER I connect to webA using HTTP, I can connect to webA using RDP ???
  7. Similar behavior can be observed in the reverse situation ( i.e. connecting to webB from network A). This is not entirely consistent since just about any direct connection, once established, can restore connectivity for other services).
  8. Some machines, but not all, of network A cannot reach web servers of network B. This seems to be firewall related (disabling the firewall seems to make it work, even if listing the rules via netsh advfirewall firewall show rule name=all does not seem to show any significant differences).
  9. this happens on other VMs too, and other protocols can sometime activate the connection : for instance connecting to an Oracle test database will unblock RDP.

This happens with or without the firewall on webA (windows firewall).

Any pointer or suggestion would be appreciated (as well as pointer to any tool that could be used to diagnose the problem).

Edit 1: : Answering the question about arp tables : (they don't change before / after )

PS C:\Users\Administrator> arp -a

Interface: 192.168.69.45 --- 0x11 Internet Address Physical Address Type 192.168.69.1 00-26-91-9c-19-57 dynamic 192.168.69.20 00-26-b9-82-ea-8d dynamic 192.168.69.23 00-24-e8-e1-31-00 dynamic 192.168.69.24 68-5d-43-0c-96-c1 dynamic 192.168.69.30 00-26-b9-82-ea-8f dynamic 192.168.69.34 00-90-f5-d6-d8-a7 dynamic 192.168.69.255 ff-ff-ff-ff-ff-ff static 224.0.0.2 01-00-5e-00-00-02 static 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.251 01-00-5e-00-00-fb static 224.0.0.252 01-00-5e-00-00-fc static 224.0.0.253 01-00-5e-00-00-fd static 224.0.1.24 01-00-5e-00-01-18 static 239.255.255.250 01-00-5e-7f-ff-fa static 255.255.255.255 ff-ff-ff-ff-ff-ff static

Interface: 10.69.12.1 --- 0x12 Internet Address Physical Address Type 10.69.12.2 00-ff-40-87-32-62 dynamic 10.69.12.3 ff-ff-ff-ff-ff-ff static 224.0.0.2 01-00-5e-00-00-02 static 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.251 01-00-5e-00-00-fb static 224.0.0.252 01-00-5e-00-00-fc static 224.0.0.253 01-00-5e-00-00-fd static 224.0.1.24 01-00-5e-00-01-18 static 239.255.255.250 01-00-5e-7f-ff-fa static

Interface: 10.69.75.6 --- 0x13 Internet Address Physical Address Type 10.69.75.5 00-ff-02-4f-94-61 dynamic 10.69.75.7 ff-ff-ff-ff-ff-ff static 224.0.0.2 01-00-5e-00-00-02 static 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.251 01-00-5e-00-00-fb static 224.0.0.252 01-00-5e-00-00-fc static 224.0.0.253 01-00-5e-00-00-fd static 224.0.1.24 01-00-5e-00-01-18 static 239.255.255.250 01-00-5e-7f-ff-fa static 255.255.255.255 ff-ff-ff-ff-ff-ff static PS C:\Users\Administrator>

Edit 2:

as i rebooted this morning, I rechecked :

  1. ping srv-sinv3 ==> OK <== well tcp/ip works
  2. telnet srv-sinv3 3389 ==> KO
  3. telnet srv-sinv3 80 ==> OK <== well tcp/ip works
  4. telnet srv-sinv3 3389 ==> OK <=== ??? WHY connecting to port 80 (IIS) sudendly unlocks 3389 ?
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  • As a possible troublesthooting step, could you get your ARP table while the connection isn't working, then again when it is working?
    – Reaces
    Dec 16, 2014 at 15:32
  • I edited the original post to add this information. Dec 17, 2014 at 9:40
  • What does netstat -a -b show? Is the svchost.exe listening? does prcomon.exe (option: show network activity) show any activity? Dec 17, 2014 at 11:26

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