Comprehensive and Detailed Explanation From Exact Extract:

In secure or isolated network segments, DHCP may be disabled to reduce the risk of unauthorized device connections or to maintain strict IP assignment control. In such cases, the help desk technician must manually configure IP settings (including IP address, subnet mask, gateway, and DNS servers). This ensures the workstation communicates properly within that segment.

A. DNS server restriction is unrelated to manual IP configuration.

B. Allow lists refer to traffic access, but manual IP assignment is due to lack of DHCP, not allow lists.

D. NAC servers control access but don't replace the need for IP addressing.