I frequently use the Cisco 2600 & 2800 series routers to connect serial devices to a TCP/IP network. For example, I will connect the serial interface of a modem to the Cisco router and then create a reverse telnet connection from the TCP/IP network to the appropriate TTY port on the router to communicate with that modem. By default, when I enable one of the async. lines on the router, it opens 4 different ports (2000, 4000, 6000, & 9000 + tty line; so for example, for tty1 it would open 2001, 4001, 6001 and 9001). I understand all of these different ports are for different modes if you will. I only need the 4000 port numbers, which are basically raw data mode. I am trying to 'harden' these devices and disable any non-necessary ports. Is there a way to enable a line, but not open all 4 of those ports?
I have this problem too.