JN0-106 Practice Test 17 — 15 Questions

Question 1

An engineer suspects that a recent software upgrade caused a compatibility issue. Which command should be used to revert the Junos OS to the previous version?

Accepted Answer

request system software rollback. The 'request system software rollback' command is the correct method to revert the Junos OS to the previously installed version. This command triggers a reboot and loads the previous software set from the /altroot partition, effectively undoing the upgrade while preserving the configuration.

Answer

rollback 0

Answer

request system reboot

Answer

request system software delete jinstall-*.tgz

Question 2

A router has an OSPF route to 10.10.10.0/24 with preference 10 and a static route to the same prefix with preference 5. Which route is active in the routing table?

Accepted Answer

The static route. In Junos, the active route in the routing table is determined by the route preference (administrative distance). A lower preference value indicates a more trusted route. Here, the static route has a preference of 5, which is lower than the OSPF route's preference of 10, so the static route is preferred and becomes active.

Answer

The OSPF route

Answer

Neither route

Answer

Both routes

Question 3

Refer to the exhibit. If the administrator now enters the command 'delete interfaces ge-0/0/0 unit 0 family inet address 192.168.1.1/24' and then commits, what will be the result?

Accepted Answer

Only the address 192.168.1.1/24 will be removed, and 192.168.1.2/24 will remain.. The 'delete' command in Junos is hierarchical and targets the exact configuration hierarchy specified. In this case, the command specifies 'address 192.168.1.1/24' under 'family inet', so only that specific address is removed. The other address (192.168.1.2/24) remains because it is a separate leaf under the same 'address' statement and is not affected by the deletion.

Answer

The commit will fail due to an attempt to delete a non-existent address.

Answer

The entire unit 0 will be deleted.

Answer

Both addresses will be removed from the configuration.

Question 4

Based on the exhibit, what is the most likely reason for the ping failure?

Accepted Answer

The neighbor device is not configured or is unreachable.. The ping failure is most likely due to the neighbor device not being configured or unreachable because the output shows the interface is up (Physical link is Up) and the unit is enabled (Unit 0 is enabled), but there is no neighbor discovery or ARP entry. Without a valid next-hop or neighbor reachability, ICMP echo requests cannot be forwarded, resulting in ping failure.

Answer

A firewall filter is blocking ICMP traffic.

Answer

The interface is disabled at the unit level.

Answer

The interface is administratively down.

Question 5

An administrator wants to view the current operational status of interface ge-0/0/1 on a Junos device. Which command displays this information?

Accepted Answer

show interfaces terse ge-0/0/1. The 'show interfaces terse ge-0/0/1' command displays a concise, one-line summary of the operational status of the specified interface, including its administrative and link state, protocol status, and configured IP addresses. This is the correct command for viewing the current operational status because 'terse' filters the output to show only the essential operational details without configuration data.

Answer

show configuration interfaces ge-0/0/1

Answer

monitor interface ge-0/0/1

Answer

show interface ge-0/0/1

Question 6

An administrator is in configuration mode and wants to see only the interfaces configuration block while editing. Which command will display just that section?

Accepted Answer

show interfaces. In Junos configuration mode, the 'show interfaces' command displays only the interfaces configuration block without leaving configuration mode. This is a Junos-specific feature where 'show' commands within configuration mode show the current candidate configuration, not operational state. The command filters the output to show only the 'interfaces' hierarchy, allowing the administrator to review just that section.

Answer

show

Answer

display set | match interfaces

Answer

run show interfaces

Question 7

Refer to the exhibit. The network administrator made a change that caused connectivity loss. They need to revert to the configuration before the most recent commit. Which command would accomplish this?

Accepted Answer

rollback 1. In Junos, rollback numbers are stored with 0 being the most recent committed configuration. To revert to the configuration before the most recent commit, you need to load the configuration that was active before that change. That is rollback 1, which represents the second most recent commit. Using rollback 0 would load the configuration that caused the issue, not fix it.

Answer

rollback 0

Answer

rollback 3

Answer

rollback 2

Question 8

A Juniper device is running out of disk space on the /var partition. Which command can be used to check disk usage?

Accepted Answer

show system storage. The correct command to check disk usage on a Juniper device is 'show system storage'. This command displays detailed information about disk partitions, including total, used, and available space, as well as the percentage of usage for each mounted filesystem, such as /var. It is the standard operational mode command for monitoring storage utilization in Junos OS.

Answer

show system disk-space

Answer

show system memory

Answer

show system resource

Question 9

A network administrator is trying to configure a firewall filter on a Juniper device. They enter configuration mode and type 'set firewall family inet filter BLOCK-ICMP term 1 from protocol icmp'. They then type 'set firewall family inet filter BLOCK-ICMP term 1 then reject'. After committing, they notice that ICMP traffic is not being blocked. They run 'show configuration firewall' and see the filter is present. They run 'show firewall filter BLOCK-ICMP' to see the counters and notice the packet count is zero. What is the most likely reason?

Accepted Answer

The filter is not applied to any interface.. A firewall filter in Junos must be applied to an interface to take effect. Simply configuring the filter under the 'edit firewall' hierarchy does not activate it; the filter must be referenced with a 'family inet' statement under the interface configuration (e.g., 'set interfaces ge-0/0/0 unit 0 family inet filter input BLOCK-ICMP'). Without this application, the filter exists in the configuration but never processes traffic, resulting in zero packet counts.

Answer

The protocol icmp is not correct; it should be 'icmp6'.

Answer

The term 'then reject' should be 'then discard'.

Answer

The filter must be applied under the 'edit firewall' hierarchy.

Question 10

A network engineer needs to add an additional IP address to an interface that already has a primary IP configured. Which method should be used?

Accepted Answer

set interfaces ge-0/0/0 unit 0 family inet address 10.0.0.2/24 secondary. In Junos, to add an additional IP address to an interface that already has a primary IP configured, you must append the 'secondary' keyword to the address configuration statement. This allows multiple IPv4 addresses on the same logical interface unit, with the first address assigned being the primary and subsequent addresses marked as secondary.

Answer

set interfaces ge-0/0/0 unit 0 family inet address 10.0.0.2/24

Answer

set interfaces ge-0/0/0 unit 0 family inet secondary address 10.0.0.2/24

Answer

set interfaces ge-0/0/0 unit 0 family inet address 10.0.0.2/24 primary

Question 11

A junior engineer is troubleshooting connectivity issues and wants to trace the path packets take to a remote destination. Which Junos command should be used?

Accepted Answer

traceroute. The 'traceroute' command in Junos is specifically designed to trace the path packets take to a remote destination by sending UDP probes with increasing TTL values and analyzing ICMP Time Exceeded messages from intermediate routers. This directly addresses the junior engineer's need to map the Layer 3 path and identify where connectivity failures occur.

Answer

monitor traffic

Answer

show route

Answer

ping

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

An administrator observes that the router's CPU utilization is consistently high. Which command helps identify which process is consuming the most CPU?

Accepted Answer

show system processes extensive. 'show system processes extensive', is correct because it displays detailed CPU utilization statistics for each running process on a Junos device, including the percentage of CPU time consumed. This allows the administrator to identify which specific process (e.g., routing protocol daemon, SNMP, or management process) is causing the high CPU load, enabling targeted troubleshooting.

Answer

show log messages

Answer

show system resource

Answer

show chassis routing-engine

Question 14

An administrator wants to verify that BGP neighbors are established. Which command provides a summary of all BGP peer sessions?

Accepted Answer

show bgp summary. The 'show bgp summary' command is correct because it provides a concise, one-line-per-peer overview of all BGP sessions, including the peer IP address, AS number, state (e.g., Established), and counters for prefixes received. This is the standard command in Junos for quickly verifying that all BGP neighbors are in the Established state without the detailed per-neighbor output.

Answer

show bgp neighbor

Answer

show interfaces terse

Answer

show route protocol bgp

Question 15

An administrator wants to view the differences between the current candidate configuration and the last committed configuration. Which command displays this?

Accepted Answer

show | compare. The 'show | compare' command displays the differences between the candidate and the active (committed) configuration.

Answer

show configuration

Answer

commit check

Answer

rollback ?