A new server was installed for the purpose of monitoring network traffic. The network has been configured in such a way that all traffic will be mirrored out the port this server is connected to…

NIC filtering is not a standard networking term in this context and does not describe the mechanism that controls whether a NIC processes all traffic on a segment.

Port security is a switch feature that restricts which MAC addresses can communicate on a port and does not control whether a connected NIC processes all mirrored traffic.

By default, a NIC discards frames not addressed to it, so the monitoring server only logs traffic destined to itself. Promiscuous mode instructs the NIC driver to pass all received frames up to the OS regardless of destination MAC address, which is required for packet capture and network traffic analysis tools to function correctly.

If the NIC were already in promiscuous mode, the server would be seeing all mirrored traffic, which is the desired outcome, not the problem described.