I have setup a firewall port-forwarding rule that allows me to RDP into my home machine from work. However, I want to allow RDP traffic (so TCP port 3389) only from my work IP since it's static (and to prevent brute-force attacks from the internet). However, for some reason I cannot change the "source address" field in the firewall rule. It is set to 'any' currently, but when I try and change it, there is a circle with a line thru it (a "no" symbol) over the cursor.
Worth noting that this is a Firewall > NAT rule, so I also tried to edit it there (under Firewall / NAT / Port Forward). However, this does not work either and displays the same "no" symbol over the cursor. I can change the source to "WAN address" but I cannot actually set the WAN address. What am I doing wrong here? Thanks.