When I scan an external IP address with Nmap my router always reboots itself, sometimes I even have to manually restart it by using the power switch.
The command I usually use is:
nmap -p 1-65535 -T4 -A -v -Pn *IP address*
I'm using an Asus RT-AC66U with the latest firmware. I have also tried using the Asuswrt-Merlin firmware but the result is still the same.
Has anyone else experienced this problem and solved it?