What could be the reason a DHCP server configured on a LAN interface does not start?

A DHCP server cannot run on a LAN interface that is also a bridge port because when an interface is part of a bridge, it essentially becomes a switching entity rather than a routed interface. In a bridged setup, the DHCP server would not have the necessary direct access to the IP layer communication on that port, which is essential for DHCP operations, such as broadcasting requests for leases. The bridging eliminates the typical behavior of layer 3 routing, which DHCP relies on to manage its address assignment process. Therefore, for a DHCP server to operate correctly, it must be configured on an interface that is not part of any bridge, ensuring proper management of DHCP traffic.

Other options, while they describe scenarios that might lead to issues with DHCP functionality under different circumstances, do not directly address the structural limitation imposed by the bridge.