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Juniper

JN0-102 · Question #183

Which two statements are true about the primary address on an interface? (Choose two.)

The correct answer is A. It is the address used by default as the local address for broadcast and multicast packets sourced C. It can be useful for selecting the local address used for packets sent out of unnumbered interfaces. The primary address on a Junos interface serves as the default local source for broadcast and multicast packets and is useful for unnumbered interfaces to select a consistent source address.

Configuration Basics

Question

Which two statements are true about the primary address on an interface? (Choose two.)

Options

  • AIt is the address used by default as the local address for broadcast and multicast packets sourced
  • BYou use the primary address when you have multiple IP addresses belonging to the same subnet
  • CIt can be useful for selecting the local address used for packets sent out of unnumbered interfaces
  • DBy default, the primary address on an interface is selected as the numerically highest local address

How the community answered

(37 responses)
  • A
    92% (34)
  • B
    5% (2)
  • D
    3% (1)

Why each option

The primary address on a Junos interface serves as the default local source for broadcast and multicast packets and is useful for unnumbered interfaces to select a consistent source address.

AIt is the address used by default as the local address for broadcast and multicast packets sourcedCorrect

The primary address configured on an interface is indeed used by default as the local source address for any broadcast and multicast packets originating from that interface.

BYou use the primary address when you have multiple IP addresses belonging to the same subnet

While a primary address can be configured when multiple IP addresses are on an interface, the primary address is not exclusively for multiple IP addresses belonging to the *same* subnet; it defines the main address for the interface regardless of subnet counts.

CIt can be useful for selecting the local address used for packets sent out of unnumbered interfacesCorrect

When an interface is configured as unnumbered, it borrows its IP address from another interface, and the primary address of the donor interface is typically used as the local address for packets sourced by the unnumbered interface.

DBy default, the primary address on an interface is selected as the numerically highest local address

By default, Junos OS selects the numerically *lowest* local address configured on an interface as the primary, not the highest.

Concept tested: Junos interface primary address functions

Source: https://www.juniper.net/documentation/us/en/software/junos/junos-interfaces/topics/concept/interfaces-multpl-addresses-overview.html

Topics

#interface configuration#IP addressing#primary address

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