Juniper Networks Certified Associate Junos JNCIA-Junos JN0-106 Questions 151–156 | Page 3/3

151

MCQhard

You are a network engineer for a large enterprise deploying a new data center using a spine-and-leaf architecture with Juniper QFX5100 switches. The underlay network uses OSPF for loopback reachability, and the overlay uses EBGP for EVPN. The leaf switches are configured as VTEPs (Virtual Tunnel Endpoints). One of the leaf switches, leaf-03, cannot establish OSPF adjacency with its spine switch, spine-01. The interfaces are up/up and the IP addresses are correctly configured. 'show ospf neighbor' on leaf-03 returns nothing. 'show ospf interface' shows the interface is in state DOWN. Both switches are configured with the same OSPF area (0.0.0.0) and the same hello interval (10 seconds). The MTU on both sides is 1500. Authentication is not configured. The spine switch has multiple OSPF neighbors from other leaves. The network is in production and other leaf switches are working fine. What is the most likely cause of the problem?

A.The OSPF network type is not consistent between the two switches.

B.The interface MTU is misconfigured on one side.

C.OSPF is disabled on the interface at the leaf switch.

D.Duplicate router ID on leaf-03 and spine-01.

AnswerC

If OSPF is not enabled on the interface, the OSPF interface state will be down.

Why this answer

The OSPF interface is in state DOWN while the physical interface is up/up, indicating that OSPF is not enabled on that interface. This can happen if OSPF is explicitly disabled under protocol configuration or if the interface is not included in the OSPF configuration. Option A is wrong because network type mismatch would not cause the interface state to be DOWN; adjacency would fail but the interface would remain UP.

Option B is wrong because MTU issues would cause OSPF adjacency problems but the interface state would be UP (not DOWN). Option D is wrong because duplicate router IDs would affect all adjacencies, not just this one, and other leaves are working fine.

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152

Multi-Selecteasy

Which THREE modes can be used to enter configuration mode in Junos? (Choose three.)

Select 3 answers

A.configure static

B.configure private

C.configure shared

D.configure dynamic

E.configure exclusive

AnswersB, C, E

Creates a private copy of the candidate configuration.

Why this answer

'configure private' creates a private configuration session that isolates candidate changes from other users, allowing multiple users to stage changes simultaneously without interference. This mode is one of the three standard configuration modes in Junos, alongside exclusive and shared.

Exam trap

The trap here is that candidates may confuse Junos configuration modes with Cisco IOS configuration modes (like 'configure terminal' or 'configure memory'), leading them to select non-existent options like 'configure static' or 'configure dynamic'.

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153

MCQmedium

Refer to the exhibit. A host connected to ge-0/0/1 cannot reach a host connected to ge-0/0/2 even though both are in VLAN10. What is the most likely cause?

A.VLAN10 is not defined in the global VLAN configuration.

B.The hosts are configured with IP addresses on different subnets.

C.An IRB interface for VLAN10 is not configured.

D.The interface ge-0/0/2 is configured as a trunk port.

AnswerB

They can't communicate at Layer 2? Actually Layer 2 doesn't care about IP. So this is tricky. Actually within same VLAN, IP subnet must match for Layer 3, but Layer 2 should work. However if hosts are on different subnets, they need a router. But the question says 'cannot reach' - likely they try to ping. If on different subnets, they need default gateway. So the most likely cause is they are on different subnets and no gateway. Alternatively, the switch might have port security. But given typical JNCIA, this is plausible.

Why this answer

Although both hosts are in the same VLAN and can communicate at Layer 2 (MAC addresses), IP communication requires them to be on the same IP subnet. If the hosts have IP addresses on different subnets, they will attempt to use a default gateway for routing. Without a router or IRB interface configured, the traffic cannot be delivered, leading to unreachability.

Exam trap

The trap here is that candidates often assume VLAN membership alone guarantees IP connectivity, overlooking the fact that IP communication requires the hosts to be in the same IP subnet or have a router to forward traffic between subnets.

How to eliminate wrong answers

Option A is wrong because VLAN10 does not need to be globally defined in the VLAN configuration for it to function; VLANs can be created dynamically on trunk ports or by simply assigning interfaces to a VLAN ID. Option C is wrong because an IRB (Integrated Routing and Bridging) interface is only required for Layer 3 routing between VLANs or for the VLAN to have an IP address for management; hosts within the same VLAN can communicate at Layer 2 without any IRB. Option D is wrong because if ge-0/0/2 were configured as a trunk port, it could still carry VLAN10 traffic as long as VLAN10 is allowed on that trunk; the trunk configuration alone does not prevent communication between hosts in the same VLAN.

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154

MCQmedium

A network operations team has received a new Juniper router to replace an existing legacy router. The team needs to apply a baseline configuration that includes system settings, interfaces, and security policies. The configuration is provided as a text file containing Junos configuration hierarchy syntax (e.g., 'system { host-name... }'). The engineer connects to the console and sees the prompt 'root@%'. What is the most efficient way to apply the configuration?

A.Use the 'load set' command to load a set of configuration commands.

B.Use FTP to transfer the file and then commit.

C.Enter configuration mode and manually type each command.

D.Use the 'load merge' command to merge the configuration file.

AnswerD

The 'load merge' command is the correct choice because it reads a configuration file in the Junos hierarchy format and merges its contents into the current candidate configuration. This is the standard way to apply a full or partial configuration file without wiping out existing settings; overlapping statements are updated while untouched parts remain intact. After the merge, the candidate can be reviewed and then committed with 'commit'.

Why this answer

The engineer is at the shell prompt (root@%), not in configuration mode. The 'load merge' command is used within configuration mode to merge a configuration file (in Junos hierarchy syntax) into the candidate configuration, which is the most efficient way to apply a pre-written baseline configuration without manual typing or complex file transfers.

Exam trap

The trap here is that candidates may confuse the shell prompt (root@%) with the configuration mode prompt (root@#) and attempt to use 'load merge' directly at the shell, which fails; they must first enter configuration mode with 'configure' or 'edit' before loading the file.

How to eliminate wrong answers

Option A is wrong because 'load set' is used to load a file containing 'set' commands (flat format), not the hierarchical configuration syntax provided; using it on a hierarchy file would cause syntax errors. Option B is wrong because FTP transfer is unnecessary and inefficient; Junos supports loading configuration files directly from local storage or via SCP/HTTP, and FTP adds security risks and extra steps. Option C is wrong because manually typing each command is time-consuming and error-prone, defeating the purpose of having a pre-written configuration file.

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155

Multi-Selectmedium

Which two events typically trigger a change to the routing table? (Choose two.)

Select 2 answers

A.Interface state change

B.System uptime

C.Log file rotation

D.BGP neighbor reset

E.Configuration commit

AnswersA, D

An interface state change (up or down) is a primary trigger for routing table updates. When an interface transitions, the kernel notifies rpd, which immediately adds or removes the directly connected route for that subnet; this change in turn causes the routing table to recalculate and, if necessary, sends updated route information to dynamic routing protocols like OSPF or IS-IS.

Why this answer

An interface state change (up/down) directly affects the reachability of directly connected networks. When an interface goes up, Junos adds the corresponding directly connected route to the routing table; when it goes down, the route is removed. Similarly, a BGP neighbor reset causes the BGP session to be torn down and re-established, which triggers the withdrawal and re-advertisement of all BGP routes, thereby modifying the routing table.

Exam trap

The trap here is that candidates often confuse a configuration commit (option E) with an automatic routing table change. A commit only activates the configuration; it does not directly modify the routing table unless the configuration itself triggers a protocol event or interface change.

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156

MCQeasy

You are a junior network engineer tasked with upgrading the Junos OS on a pair of EX3400 switches that are in a Virtual Chassis. You have downloaded the new software image to the primary switch. Before performing the upgrade, you must verify the image's integrity and check the current version. Which sequence of commands should you use?

A.Run 'show system uptime' and then 'request system software add /var/tmp/junos-new.tgz'.

B.Run 'show system software' and then 'request system software add validate'.

C.Run 'show version' and then 'request system software validate /var/tmp/junos-new.tgz'.

D.Run 'show configuration system software' and then 'file checksum sha256 /var/tmp/junos-new.tgz'.

AnswerC

This is the correct approach because 'show version' first confirms the currently running Junos image and software version, which is essential for comparing against the new package and verifying upgrade path compatibility. Then 'request system software validate /var/tmp/junos-new.tgz' performs a dry-run validation of the image file, checking its integrity, checksum, and compatibility with the current system without actually installing it. Together, these two commands give the engineer a clear picture of the current state and a verified upgrade package before installation.

Why this answer

'show version' displays the current Junos OS version running on the switch, which is necessary to confirm the starting point before an upgrade. Then 'request system software validate /var/tmp/junos-new.tgz' performs a checksum verification and package integrity check on the image file without installing it, ensuring the image is not corrupted. This sequence directly addresses the two tasks: verifying the image's integrity and checking the current version.

Exam trap

The trap here is that candidates confuse 'show system software' (a non-existent command) with 'show version', or think that 'file checksum sha256' alone is sufficient for integrity verification, missing the fact that Junos requires the full 'request system software validate' command to perform a comprehensive package check before installation.

How to eliminate wrong answers

Option A is wrong because 'show system uptime' shows how long the switch has been running, not the current software version, and 'request system software add /var/tmp/junos-new.tgz' immediately installs the image without any integrity validation. Option B is wrong because 'show system software' is not a valid Junos command (the correct command is 'show version' or 'show system software information'), and 'request system software add validate' is syntactically incorrect—the correct syntax is 'request system software validate <filename>'. Option D is wrong because 'show configuration system software' displays the software-related configuration (e.g., licenses), not the current running version, and while 'file checksum sha256' does verify integrity, it only checks the hash and does not perform the full package validation that 'request system software validate' does, nor does it check the current version.

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Juniper Networks Certified Associate Junos JNCIA-Junos (JN0-106) — Questions 151–156