bobmay

To open a port on a router simply means to enable it. In the Cisco IOS one would use the comand "shutdown" to turn off a port, and "no shutdown" to turn on, or "open a port".
See below:

The shutdown command disables all functions on the specified interface. On serial interfaces, this command causes the DTR signal to be dropped. On Token Ring interfaces, this command causes the interface to be deinserted from the ring. On FDDI interfaces, this command causes the optical bypass switch, if present, to go into bypass mode.

This command also marks the interface as unavailable. To check whether an interface is disabled, use the EXEC command show interfaces. An interface that has been shut down is shown as administratively down in the display from this command.

Examples

The following example turns off Ethernet interface 0:

interface ethernet 0
shutdown


The following example turns the interface back on:

interface ethernet 0
no shutdown