JN0-106 User Interfaces Practice Test 4 — 15 Questions

Question 1

You are a network engineer for a service provider that recently deployed a Juniper MX router at a new Point of Presence (PoP). The router is used to aggregate customer connections and exchange routes with upstream providers via BGP. After the initial configuration, you notice that the router is not learning any routes from one of the upstream BGP peers. You have verified that the BGP session is established (state Established) and that the peer is sending routes. You suspect that the issue might be related to the firewall filter or routing policy. You want to determine if any inbound routes are being rejected and why. Which command would provide the most direct information about why routes are being rejected?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

show route receive-protocol bgp 192.0.2.1. 'show route receive-protocol bgp 192.0.2.1', is correct because it displays the exact routes received from a specific BGP peer along with any policy or filter actions applied (e.g., reject, accept). This command directly shows whether routes are being rejected and the reason (e.g., due to an import policy or firewall filter), making it the most direct diagnostic tool for the described issue.

Answer

show route protocol bgp

Answer

show bgp summary

Answer

show firewall filter <filter-name>

Question 2

You are managing a Juniper EX4300 switch that serves as a Layer 3 access switch for a campus network. The switch has multiple VLANs configured with IRB interfaces. Users in VLAN 10 report that they cannot reach the default gateway (IRB.10) even though other VLANs are working fine. You check the configuration and see that interface irb.10 is configured with an IP address. You also verify that the VLAN is associated with the correct access ports. However, when you ping the IRB.10 address from the switch itself, it fails. You suspect that the issue might be that the IRB interface is not 'up'. Which command would you use to quickly verify the operational status of the IRB interface?

Accepted Answer

show interfaces terse irb.10. `show interfaces terse irb.10` displays the operational status (up/down) of the IRB interface along with its configured IP address. Since the issue is that the IRB interface may not be 'up', this command quickly confirms whether the interface is operationally active, which is essential for Layer 3 forwarding.

Answer

show ethernet-switching table

Answer

show configuration interfaces irb.10

Answer

show vlan

Question 3

A network engineer needs to view the operational status of all interfaces on a Junos device, including those that are disabled. Which command should be used?

Accepted Answer

show interfaces terse. The 'show interfaces' command displays detailed information for all interfaces, including those that are administratively disabled. However, 'show interfaces terse' provides a concise, one-line-per-interface summary that is more efficient for quickly viewing the operational status of all interfaces, including disabled ones. For the JNCIA exam, 'show interfaces terse' is the recommended command for this purpose because it offers a clear and compact overview of interface status across the device.

Answer

show interfaces

Answer

show configuration interfaces

Answer

monitor interface traffic

Question 4

You are a junior network engineer at a company that uses Juniper MX routers. You are troubleshooting a connectivity issue on a branch router. The branch router has two upstream links to the corporate network: ge-0/0/0 (10.1.1.1/30, connected to core router A) and ge-0/0/1 (10.1.1.5/30, connected to core router B). The branch router runs OSPF and has a default route learned from both upstream routers. The routing table shows two equal-cost default routes via both next hops. However, traffic from the branch to the corporate network is experiencing intermittent high latency and some packet loss. You suspect that asymmetric routing is causing issues because the return traffic is not following the same path. You want to influence the router to prefer one upstream link for all traffic to the corporate network. You have decided to adjust the OSPF metric on the branch router to make the link to core router A more preferred. You are in configuration mode on the branch router. Which single configuration change will accomplish this goal?

Accepted Answer

set protocols ospf area 0 interface ge-0/0/1 metric 200. Setting the OSPF metric on interface ge-0/0/1 to a higher value (200) increases the cost of that link, making the default route via ge-0/0/0 (which retains the default OSPF metric of 1 on a Gigabit Ethernet interface) more preferred. This influences the branch router to use the lower-cost path through core router A for all traffic to the corporate network, resolving asymmetric routing issues.

Answer

set interfaces ge-0/0/1 unit 0 family inet cost 200

Answer

set protocols ospf area 0 interface ge-0/0/1 passive

Answer

set interfaces lo0 unit 0 family inet address 10.0.0.1/32 metric 100

Question 5

A technician is troubleshooting a routing issue and needs to see real-time updates of BGP prefixes being received. Which command should be used?

Accepted Answer

monitor route bgp. The 'monitor route bgp' command in Junos OS provides a real-time, continuously updated view of BGP routes as they are learned or withdrawn. Unlike static show commands, this monitor command refreshes the output dynamically, making it ideal for observing live BGP prefix updates during troubleshooting.

Answer

monitor traffic interface ge-0/0/0

Answer

show route advertising-protocol bgp

Answer

show route protocol bgp

Question 6

During a maintenance window, an engineer needs to apply a configuration change that reverts automatically if the commit fails or the administrator does not confirm within a set time. Which feature should be used?

Accepted Answer

commit confirmed. The 'commit confirmed' feature allows an engineer to apply a configuration change that automatically reverts to the previous configuration if the commit is not confirmed within a specified time period (default 10 minutes). This ensures that if the commit fails or the administrator loses connectivity, the system rolls back safely without manual intervention.

Answer

commit check

Answer

commit synchronize

Answer

commit at 03:00

Question 7

After upgrading Junos, a router fails to boot with a file system error. The admin needs to recover the system from the backup partition. Which key should be pressed during boot to access the boot menu?

Accepted Answer

Space. Pressing the Space bar during the boot process on a Juniper device interrupts the normal boot sequence and presents the boot menu. From this menu, the administrator can select the backup Junos partition (typically labeled as '1' or 'backup') to recover the system when the primary partition has a file system error.

Answer

Ctrl+C

Answer

Esc

Answer

Enter

Question 8

A user wants to ensure that a configuration change is applied across both Routing Engines in a dual-RE system. Which command must be used?

Accepted Answer

commit synchronize. The 'commit synchronize' command applies the candidate configuration to both Routing Engines simultaneously in a dual-RE system. This ensures configuration consistency across the master and backup RE, which is critical for high availability and seamless failover in Junos.

Answer

commit and-quit

Answer

commit confirmed

Answer

commit full

Question 9

An administrator needs to see which interfaces are configured and their current operational status in a concise format. Which command provides this information?

Accepted Answer

show interfaces terse. The 'show interfaces terse' command displays a concise, table-like output listing all interfaces (including logical units) along with their administrative status (up/down) and operational status (up/down). This is the most efficient way to see both configured interfaces and their current state in a compact format, as required by the question.

Answer

show interfaces

Answer

show configuration interfaces

Answer

show interfaces descriptions

Question 10

An engineer needs to view the current operational state of the device, including system uptime, CPU load, and memory usage. Which two commands would provide this information? (Choose two.)

Accepted Answer

show system uptime. Option B, 'show system uptime,' is correct because on Junos devices this command reports the current time, how long the device has been running (system uptime), and the load averages for 1, 5, and 15 minutes, directly satisfying the uptime and CPU load requirements. Option D, 'show system memory,' is correct because it displays memory utilization statistics, including total, used, and free memory, which fulfills the memory usage portion of the request. Option A, 'show system processes,' lists running processes and their CPU/memory consumption per process rather than the overall system uptime and aggregate load, so it does not match the scenario as directly. Option C, 'show system storage,' reports disk and filesystem space usage, not CPU load or memory, and Option E, 'show chassis hardware,' displays hardware inventory and component information, neither of which provides the requested operational state.

Answer

show system processes

Answer

show system storage

Answer

show chassis hardware

Question 11

A junior administrator is learning to navigate the Junos CLI. Which three statements about CLI modes are correct? (Choose three.)

Accepted Answer

Operational mode is indicated by a > prompt.. Option A is correct because Junos operational mode is indeed identified by the '>' prompt (e.g., user@host>), which is where monitoring and show commands are executed. Option B is correct because the 'configure' command is the standard way to enter configuration mode from operational mode, changing the prompt to '#' (e.g., user@host#). Option E is correct because from configuration mode you can run operational commands by prefixing them with 'run', such as 'run show interfaces', without leaving configuration mode. Option C is incorrect because 'commit' is only available in configuration mode, not operational mode. Option D is incorrect because the proper way to return to operational mode is the 'exit' command (or 'exit configuration-mode' in some contexts), not 'exit configuration'.

Answer

The 'commit' command is available in both operational and configuration modes.

Answer

You can switch from configuration mode to operational mode using the 'exit configuration' command.

Question 12

Refer to the exhibit. An administrator sees the following configuration output. What is the purpose of the 'description' statement in this context?

Accepted Answer

It sets the interface description visible in 'show interfaces description'.. In Junos, the 'description' statement under an interface configuration sets a text string that is displayed in the output of 'show interfaces description'. This is the standard way to provide a human-readable label for the interface, such as 'Link to Core Router A'. It does not affect SNMP, administrative comments, or syslog tags.

Answer

It sets the SNMP ifAlias to the interface's MAC address.

Answer

It sets the administrative comment visible in the config.

Answer

It sets the interface's syslog tag.

Question 13

Refer to the exhibit. An engineer notices high error counts on the interface. Based on the output, what is the most likely cause?

Accepted Answer

The interface is connected to a device configured for half-duplex.. The output shows high error counts on the interface, which is a classic symptom of a duplex mismatch. When one end of an Ethernet link operates in full-duplex and the other in half-duplex, collisions occur on the half-duplex side because it expects to wait for the carrier to be clear before transmitting, while the full-duplex side transmits at any time. This leads to frame check sequence (FCS) errors, alignment errors, and runts on the half-duplex interface. Option D is correct because the local interface is likely full-duplex (default on modern Juniper devices), and the connected device is configured for half-duplex, causing the mismatch.

Answer

The interface has a hardware fault.

Answer

The interface is experiencing excessive broadcasts.

Answer

The interface is operating in half-duplex mode.

Question 14

Refer to the exhibit. An administrator needs to ensure that all emergency (emerg) messages are logged to the console. Based on the configuration shown, which statement is correct?

Accepted Answer

Emergency messages are logged to all destinations.. The configuration shown includes the 'any' facility and 'emerg' severity for the console, file, and remote host destinations. In JUNOS, when a severity level is set for a syslog destination, all messages of that severity and higher are logged. Since 'emerg' is the highest severity, it applies to all configured destinations, not just one.

Answer

Emergency messages are logged to the console only.

Answer

Emergency messages are logged only to the file 'messages'.

Answer

Emergency messages are logged only to the remote host.

Question 15

An engineer needs to view the current active configuration of a Junos device without making any changes. Which CLI mode should they use?

Accepted Answer

Operational mode. Operational mode is the default CLI mode in Junos, used for monitoring, troubleshooting, and viewing the current active configuration without making any changes. Commands in this mode are read-only and do not modify the device's configuration. The active configuration is the one currently running on the device, and it can be viewed using commands like 'show configuration' in operational mode.

Answer

Privileged mode

Answer

Configuration mode

Answer

Exclusive configuration mode