Primary Address on an Interface - JN0-102 Exam Guide

AC

The correct answers are A and D.

A. It is the address used by default as the local address for broadcast and multicast packets sourced locally and sent out of the interface.

The primary address on an interface is the IP address used as the source address for packets originating from the local device and sent out of that interface. This includes broadcast and multicast packets. The primary address is also used as the destination address for ICMP packets generated by the device.

B. You use the primary address when you have multiple IP addresses belonging to the same subnet on the same interface.

This statement is not true. You cannot have multiple IP addresses belonging to the same subnet on the same interface. Each interface must have a unique IP address, and the subnet mask defines the range of addresses that can be used on that interface.

C. It can be useful for selecting the local address used for packets sent out of unnumbered interfaces when multiple non-127 addresses are configured on the loopback interface.

This statement is not true. Unnumbered interfaces do not have IP addresses assigned to them, so the concept of a primary address does not apply. Additionally, loopback interfaces are not used for packet forwarding, so the choice of IP address on the loopback interface does not affect the choice of local address used for packets sent out of other interfaces.

D. By default, the primary address on an interface is selected as the numerically highest local address configured on the interface.

This statement is true. When multiple IP addresses are configured on an interface, the primary address is selected as the numerically highest local address by default. This can be changed by explicitly specifying a different primary address using the "set interfaces <interface-name> family inet address <ip-address> primary" configuration command.