I have a cisco 1760 router which has port forwarding for ports 25, 80 and 443 for my web services. So if, let's say, I want to open a connection on port 21 of the router, it should not be allowed. The router sends a "connection refused" packet.
What I want to do, is reproduce the DROP behavior of iptables. If I open a connection on port 21, the router should not respond at all and drop the packet.
How can I achieve that?
ip address x.x.x.89 255.255.255.0
no ip unreachables
ip nat outside