How to find reason for blocked application?

Comodo Internet Security - CIS Firewall Help - CIS
1

Hi all,

I’m a long time Comodo user, but sometimes it puzzles me.
My system is well adjusted and I use a lot of TeamViewer locally via LAN and VPN.
Now I just upgraded to the new Windows 10 “Fall Creators Update” and I can’t connect to one PC through the VPN using the IP address, but it still works over the Internet with the ID.
If I disable the Comodo Firewall it works as expected as it did before the Windows 10 update, so the reason must be inside Comodo Firewall.

But where?

The Teamviewer binaries are trusted applications, no pop-ups appear and the log does not contain any information about blocked incoming connections.

I remember that I might have had such a problem in the past, but I don’t remember the solution anymore. It was of the kind “Nah, this will not gonna happen again.” 88)

Thanks for your help.

2

How are your global rules set? Also try disabling block fragmented IP traffic in firewall settings.

3

I don’t know how to explain, so I’ll post a screenshot.

“Block fragmented IP traffic” is disabled (unchecked).

4

Try enabling logging for each global block rule and add an additional block rule with logging enabled as follows: Action=Block, Protocol=IP, Direction=In; and place this block rule at the very bottom so it is the last rule in the list. Then try connecting again and check the firewall event logs to see what is being blocked.

5

Thanks a lot.
I followed your guide and got the following entries in the log.
This is rather strange, as the source IP is its own internet IP and the destination IP is its own local IP.

6

Now Change that block rule to allow and you should be able to connect.

7

I selected “Unblock” for the “Windows Operating System” application and deleted the rule.

Thanks for your help mate. :-TU