The port shows a green light as if it were connected, but the show interface status displays not connected.
A destination port (also called a monitor port) is a switch port where the Switched Port Analyzer (SPAN) sends packets for analysis. After a port becomes an active destination port, it does not forward any traffic except that required for the SPAN session. By default, an active destination port disables incoming traffic (from the network to the switching bus), unless you specifically enable the port. If incoming traffic is enabled for the destination port, it is switched in the native VLAN of the destination port. The destination port does not participate in spanning tree while the SPAN session is active.
The destination port does not transmit any traffic except that traffic required for the SPAN session unless learning is enabled. If learning is enabled, the port also transmits traffic directed to hosts that have been learned on the destination port. The up/down status is the expected state for a destination port. Use the learning keyword at the end of the SPAN destination port statement if you want this port to communicate with the network.
This output shows an example command in IOS :
Switch(config)#monitor session 1 destination interface GigabitEthernet
0/1 ingress vlan 30 learning
When ingress is enabled, the SPAN destination port accepts incoming packets and switches them normally. By default, host learning is disabled on SPAN destination ports with ingress enabled. So instead of setting a static entry on the MAC table, you can insert the learning keyword at the end of the statement as the example output here shows.
Refer to SPAN on the Catalyst 2900, 4500/4000, 5500/5000, and 6500/6000 Series Switches That Run CatOS for more information