Q. Why the TCP port 0 and 1 of Vigor Router are scanned in CLOSE status after I turn on the Block TCP flag scan function ?

Vigor Router has a special firewall mechanism which can confuse the OS Detection Tools when Vigor Router detects the the scanning (tcp flag field) is abnormal. OS detection is used to collect information like Operating System or Application type and so on by TCP/UDP flag scan tools. After enabling the "Block TCP flag scan" function, the special mechanism will not respond the scan request according to its real status. So the TCP port 0 and 1 are scanned as CLOSE is not the real status of the TCP port status of Vigor Router but the fake status to annoy the scanner. If you don??t want to activate the mechanism or you want to let Vigor router respond the real port status, you may disable the "Block TCP flag scan" feature.

Please go to the page of "Firewall>>DoS defense Setup" to disable the "Block TCP flag scan" option.