sorry, forget that - I found it:
In order to configure port Fa0/1 as a destination port, the source ports Fa0/2 and Fa0/5, and the management interface (VLAN 1), select the interface Fa0/1 in the configuration mode:
Switch(config)#interface fastethernet 0/1
Enter the list of ports to be monitored:
Switch(config-if)#port monitor fastethernet 0/2
Switch(config-if)#port monitor fastethernet 0/5