How can you configure three interfaces into one single physical interface in Junos?

The concept of configuring multiple interfaces into one single logical interface in Junos relates to the use of logical units, which are a way to segment or differentiate traffic on a single physical interface. When using logical units, you can create sub-interfaces on a physical interface that can be assigned different IP addresses, VLAN tags, and other configurations, effectively making it possible to manage and route multiple traffic types over a single physical medium.

Logical units allow for efficient use of hardware resources since you can consolidate the management of several network connections into a single physical interface without needing additional hardware. This can also simplify configuration and maintenance of the network since you can handle multiple network addresses and policies through one port.

In contrast, while link aggregation refers to combining multiple physical interfaces to create a single logical link for load balancing and redundancy purposes, it does not create separate logical paths but instead increases throughput for the existing connections. Aggregated Ethernet is a specific type of link aggregation in Junos, and static routing is not relevant here as it pertains to routing methods, not interface configuration. Therefore, logical units is the specific solution that fits the requirement of configuring multiple interfaces under one single physical interface.