A server administrator is configuring a new server for an organization. The server will function as a firewall and proxy server, as well as provide NAT services for other devices on the network…

A firewall and NAT server must be multi-homed with at least two NICs: one NIC connected to the inside (private/LAN) network and one connected to the outside (public/internet) network. NAT translates private IP addresses from the internal NIC to the public IP on the external NIC, which requires the network boundary to exist as a physical interface separation. This two-NIC minimum is the fundamental requirement for any device performing network address translation or perimeter security.

Configuring each NIC symmetrically with equivalent addressing does not establish the inside/outside network boundary that NAT and firewall functions require.

A single NIC with two IP addresses cannot properly enforce firewall policy or perform NAT because traffic from both network segments arrives on the same physical interface with no true separation.

Three NICs are not required for a basic firewall, proxy, and NAT deployment - a minimum of two NICs is sufficient to segment the internal and external networks.