A possible cause could be that you have network cables plugged into the wrong network interfaces on the back of the IDS-4215.
Beginning with IPS 5.0, on all existing sensor appliances, we name the network interfaces according to a Cisco standard. For a given slot (or main board) the interface physically closest to the power supply is lowest interface number (0), and the numbers increase as you move away from the power supply.
This naming convention is opposite from the silk screen interface names marked on the outside of IDS-4215 sensors.
The interface pair you call "PAIR1" includes the interface on the main board furthest from the power supply (called "FastEthernet0/1" on the command line, but which is labeled "FastEthernet0" on the back of the unit) and the third interface from the power supply on the 4FE module.
Hopefully my ASCII graphics make sense. This is what you would see looking at the rear of the IDS-4215:
O-X-O-O......X-O......PS
Each "X" or "O" represents a network interface. The Xs mark the two that are in PAIR1. "PS" is the power supply.
I recommend that you label your IDS-4215 interfaces, or blot out the silk screened names with a permanent marker, to avoid confusion in the future. We realize this causes some confusion, but moving to a naming standard will benefit you in the long run, especially if you have multiple Cisco products installed in your network.
