The specific commands vary somewhat based on the type of switch and IOS you are running. CATOS on 6509′s is probably the easiest, where you simply specify
“set span 4/1 4/48 both” to capture inbound and outbound traffic from port 4/1, and route it to 4/48.
The equivalent on IOS would be to set both span source and destination in separate commands:
monitor session 1 source interface fast 4/1
monitor sesssion 1 destination interface fast 4/48