Which statement is correct about logical units on Juniper Router interfaces?
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A. B. C. D.C
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.
Logical units (LUs) are virtual interfaces that can be created on a physical interface of a Juniper router. Each logical unit has its own configuration and routing table. Here is a detailed explanation of each answer:
A. Logical units are used only when a Layer 2 identifier is present such as a VLAN. This statement is incorrect. While logical units can be used to create VLAN interfaces, they can also be used for other purposes such as creating sub-interfaces for different customers or applications, or for dividing a physical interface into multiple logical interfaces. Therefore, logical units are not used only for Layer 2 identifiers such as VLANs.
B. A logical unit of 0 is required when using a frame-relay DLCI. This statement is partially correct. In the case of frame-relay DLCIs, a logical unit of 0 is typically used for the physical interface, and additional logical units are created for each DLCI. Therefore, a logical unit of 0 is required in this case, but additional logical units are also necessary.
C. A logical unit is always required. This statement is incorrect. Logical units are not always required. In fact, on some interfaces such as physical Ethernet interfaces, logical units are not used at all. However, on other types of interfaces such as serial or SONET/SDH interfaces, logical units are often used to create sub-interfaces.
D. Logical units are not required unless ATM or 802.1Q VLAN tagging is configured. This statement is partially correct. While logical units are often used for ATM or 802.1Q VLAN tagging, they can also be used for other purposes. Therefore, logical units are not required only when these features are configured, but they can be used in many other scenarios as well.
In summary, the correct statement is that logical units are not always required and can be used for a variety of purposes beyond Layer 2 identifiers such as VLANs. However, they are often used for creating VLAN interfaces or dividing a physical interface into multiple logical interfaces.