Which statement is correct about logical units on Juniper Router interfaces?

A.
Logical units are used only when a Layer 2 identifier is present such as a VLAN.

B.
A logical unit of 0 is required when using a frame-relay DLCI.

C.
A logical unit is always required.

D.
Logical units are not required unless ATM or 802.1Q VLAN tagging is configured.

Explanation:
Many router vendors refer to a logical unit as a subinterface; they do not require a subinterface on every
physical interface, whereas a Juniper Networks router does.
Note: All router interfaces that will send and receive transit traffic require a logical unit to be configured. This
logical unit creates a division of the physical interface into multiple parts.
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ch04s03.html