Which type of IPv4 address must be assigned to a server to protect it from external access and allow only internal users access while restricting internet access?

Private IPv4 addresses (e.g., 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) are not routable on the public internet, meaning a server assigned such an address cannot be directly accessed from outside the internal network without Network Address Translation (NAT), thus restricting external access.

Public IPv4 addresses are globally routable on the internet, which would allow direct external access to the server, contrary to the requirement.

Global unicast addresses encompass all globally unique IP addresses, including public ones, and do not inherently restrict external access.

Multicast addresses are used for one-to-many communication within a network and are not assigned to individual servers for primary addressing or to restrict external access.