I have a TZ 190 Wireless Enhanced with SonicOS Enhanced 188.8.131.52-20e.
Yesterday, people could access without any problems a bank website wich uses HTTPS. Today, it is imposible to access only that website, every other ones works without problems.
When checking the log message filtering to my IP only, this is what appears and I suspect is the cause of this problem, because all other websites are working:
Priority: Notice Category: Network Access Message: TCP handshake violation detected; TCP connection dropped Source: X.Y.Z.3, 51997, LAN (admin) Destination: 184.108.40.206, 443, WAN Notes: Handshake Timeout
Where X.Y.Z.3 is my local IP.
I've tried to change TCP Settings under Firewall option, and activated this options with no success:
Enforce strict TCP compliance with RFC 793 and RFC 1122
Enable TCP checksum enforcement
I've also tried to find the MTU and at first I got:
Packet needs to be fragmented but DF set
But when I lower the value of ping -f -l to 1468 I got:
Also I deactivate CFS in lan and wan zones. Nothing works.
Can you please help me? Any Ideas?