What is the minimum number of network connections in a multihomed firewall?

3 interfaces describe a firewall with a DMZ configuration, which is one common multihomed design but not the minimum requirement to be considered multihomed.

A multihomed host or firewall is defined as any system with more than one network interface, so the absolute minimum to qualify as multihomed is 2 connections. A dual-homed firewall with exactly 2 interfaces is the simplest multihomed configuration, typically separating an internal trusted network from an external untrusted network. Additional interfaces (for DMZ segments) increase the count beyond the minimum of 2.

5 connections exceed the minimum requirement and describe a more complex segmented network architecture, not the baseline definition of a multihomed device.

4 connections also exceed the minimum and represent an advanced multi-zone firewall design, not the minimum required for a multihomed classification.