Very weird situation these days — my server became inaccessible — randomly.

Literally “random”, like I was able to connecting to my server via IPv4, but unable after several minutes/hours. The trace result shows the connection got blocked before even reach to the China Telecom backbone 202.97.*.* (forgot to take a screenshot). Luckily, my server has IPv6 and I’m using 6in4 tunnel provided by HE, so It’s still reachable via IPv6.

And after some trying, I found the server became accessible via IPv4 after my WAN IP address changed  (I’m using a PPPoE broadband, IP address changes when re-dail), but may became inaccessible later.

Final thoughts:

I thought, this problem might be caused by my ISP which said before they were planning to expand their capacity.

Another thought, the Great F**king FireWall is upgrading or testing new features?