JN0-106 Practice Test 15 — 15 Questions

Question 1

A route learned via BGP appears as 'hidden' in the routing table. Which condition is most likely the cause?

Accepted Answer

The BGP next-hop is unreachable. In JUNOS, a BGP route is marked as 'hidden' in the routing table when the next-hop address is not reachable via any active route in the inet.0 table. This is a fundamental BGP path selection prerequisite: the next-hop must be resolvable (typically via an IGP or static route) for the route to be considered active and installed.

Answer

The BGP route has a higher AS path length than another route

Answer

The BGP route has been rejected by a policy

Answer

The BGP local preference is too high

Question 2

A network engineer sees an unknown unicast flood on a Juniper EX switch. Which mechanism is most effective at reducing such floods?

Accepted Answer

Enable storm control for unknown unicast traffic.. Unknown unicast flooding occurs when a switch does not have a MAC address entry for a destination, causing it to flood the frame out of all ports in the VLAN except the ingress port. Storm control for unknown unicast traffic (set using `set ethernet-switching-options storm-control interface <interface> unknown-unicast`) directly limits the rate of such flooded traffic, preventing excessive bandwidth consumption. This is the most effective mechanism because it specifically targets and rate-limits unknown unicast floods without altering MAC learning or aging behavior.

Answer

Configure static MAC addresses for all endpoints.

Answer

Increase the MAC address table aging time.

Answer

Disable MAC learning on trunk interfaces.

Question 3

Which two commands can be used to monitor real-time interface statistics and errors on a Junos device?

Accepted Answer

show interfaces extensive ge-0/0/0 | refresh 1. Option C, 'show interfaces extensive ge-0/0/0 | refresh 1', is correct because the 'extensive' keyword displays detailed statistics including error counters, and the '| refresh 1' pipe re-runs the command every second, giving real-time monitoring of a specific interface. Option D, 'monitor interface ge-0/0/0', is correct because the 'monitor interface' command is Junos's dedicated real-time interface statistics viewer, continuously updating counters such as packets, bytes, and errors for the named interface. Option A, 'show interfaces terse', only gives a one-time summary of interface status and addresses without error detail or refresh, so it is not real-time monitoring. Option B, 'show interfaces ge-0/0/0', provides a single snapshot of standard statistics and does not refresh or emphasize error counters. Option E, 'monitor security log', streams security log messages rather than interface statistics and errors, so it does not meet the requirement.

Answer

show interfaces terse

Answer

show interfaces ge-0/0/0

Answer

monitor security log

Question 4

A router has a directly connected route to 10.10.10.0/24 on interface ge-0/0/0.0, a static route to the same prefix with next-hop 192.168.1.1, and an OSPF route to the same prefix. Which route is active in the routing table?

Accepted Answer

The directly connected route. In Junos, the routing table (inet.0) selects the active route based on the route preference (administrative distance). Directly connected routes have a default preference of 0, which is the lowest possible value, making them preferred over static routes (default preference 5) and OSPF routes (preference 10 for intra-area, 150 for external). Therefore, the directly connected route to 10.10.10.0/24 on ge-0/0/0.0 is active.

Answer

The static route

Answer

No route is active due to multiple routes

Answer

The OSPF route

Question 5

Which TWO statements about configuration archival in Junos are true?

Accepted Answer

The 'system archival' hierarchy enables automatic backup of configurations.. The 'system archival' hierarchy in Junos is specifically designed to enable automatic backup of configuration files. This feature allows administrators to configure periodic transfers of committed configurations to a remote server, ensuring configuration history is preserved without manual intervention.

Answer

Archival stores the candidate configuration.

Answer

Archival only saves the rescue configuration.

Answer

Archival automatically archives after every commit without any configuration.

Question 6

Refer to the exhibit. Why is the static route not active?

Accepted Answer

The static route has a higher preference than the OSPF route.. Junos uses route preference (administrative distance) to select the active route when multiple routes to the same destination exist. By default, OSPF has a preference of 10, while a static route has a preference of 5. Since a lower preference value is more preferred, the static route should normally be active. However, the question indicates the static route is not active, which implies the static route's preference has been manually set higher than OSPF's preference (e.g., static route preference > 10), causing OSPF to be selected as the active route.

Answer

The OSPF route has a lower metric.

Answer

The static route's next-hop is not reachable.

Answer

The static route is not committed.

Question 7

An engineer wants to revert all uncommitted changes in the candidate configuration and start fresh from the currently active configuration. Which command should be used?

Accepted Answer

rollback 0. The `rollback 0` command reverts all uncommitted changes in the candidate configuration and restores it to match the currently active configuration (the one most recently committed). This is because Junos stores the last 50 committed configurations, with index 0 always representing the active configuration. Using `rollback 0` effectively discards any uncommitted edits and starts fresh from the last committed state.

Answer

commit check

Answer

rollback 1

Answer

load override terminal

Question 8

A network operator needs to upgrade the Junos OS on the backup RE (re1) of a dual-RE system. Which procedure ensures that only the backup RE is upgraded and rebooted without affecting the forwarding plane?

Accepted Answer

Use 'request system software add re1' and then 'request system reboot re1'. The 'request system software add re1' command installs the Junos OS image only on the backup Routing Engine (RE1), and the subsequent 'request system reboot re1' reboots only that RE. In a dual-RE system, this procedure isolates the upgrade to the backup RE, ensuring the forwarding plane remains active on the primary RE (RE0) and no traffic disruption occurs.

Answer

Use 'request system software add <image> both' and then 'request system reboot both'

Answer

Use 'request system software add <image> re0' and then 'request system reboot re0'

Answer

Copy the image to both REs and reboot the backup RE with 'request system reboot slice 1'

Question 9

Which two statements are true about static routes on Juniper devices? (Choose two.)

Accepted Answer

A static route with a next-hop of an IP address requires that the next-hop be reachable.. Option A is correct because a static route whose next-hop is specified as an IP address is only installed in the routing table (and thus active) if that next-hop is resolvable and reachable via a route in inet.0; if the next-hop is unreachable, the route stays hidden. Option B is correct because Junos supports the qualified-next-hop statement, which lets you attach a separate preference to each next-hop of a static route, enabling conditional/backup routing where the secondary next-hop is used only when the primary becomes unreachable. Option C is wrong because a static route pointing at an interface (e.g., next-hop ge-0/0/0.0) is only active while that interface is up, so it is not active when the interface is down. Option D is wrong because in Junos a lower preference value is preferred, so a route with preference 5 wins over one with preference 10. Option E is wrong because static routes can perform load balancing by configuring multiple next-hops (or multiple paths) for the same destination, which are then installed as equal-cost multipath entries.

Answer

A static route with a next-hop of an interface will be active even if the interface is down.

Answer

A static route with a preference of 10 is preferred over a static route with a preference of 5.

Answer

Static routes cannot be used for load balancing.

Question 10

Which TWO configuration statements are valid for defining a static route on a Junos device?

Accepted Answer

set routing-options static route 10.0.0.0/8 discard. Option A is correct because Junos supports the discard next-hop on a static route, which silently drops matching traffic and is configured exactly as set routing-options static route 10.0.0.0/8 discard. Option C is correct because qualified-next-hop is a valid Junos static-route next-hop type that allows a per-next-hop preference, so set routing-options static route 10.0.0.0/8 qualified-next-hop 192.168.1.1 preference 10 is syntactically valid. Option B is wrong because reject-all is not a valid Junos static-route next-hop keyword; the valid reject form is simply reject. Option D is wrong because Junos static routes do not use a metric statement; route preference is set with preference, not metric. Option E is wrong because passive is not a valid static-route option in Junos.

Answer

set routing-options static route 10.0.0.0/8 reject-all

Answer

set routing-options static route 10.0.0.0/8 next-hop 192.168.1.1 metric 10

Answer

set routing-options static route 10.0.0.0/8 passive

Question 11

Which TWO factors are directly used when comparing route preferences in JunOS? (Choose two.)

Accepted Answer

Metric (or cost). In Junos, route preference (also called administrative distance) is the primary tie-breaker used to compare routes from different protocols, so option E (Preference value) is directly used — lower preference wins, e.g., direct=0, static=5, OSPF internal=10, RIP=100. When two routes come from the same protocol, the protocol's metric/cost is compared, so option C (Metric or cost) is also directly used, e.g., OSPF cost or RIP hop count. Option A (Next-hop reachability) is a validity condition for installing a route, not a comparison factor between competing routes. Option B (Number of hops) is only a metric within protocols like RIP, not a universal Junos comparison factor. Option D (Prefix length) is used for longest-match forwarding lookups in the forwarding table, not for route preference comparison in the routing table.

Answer

Next-hop reachability

Answer

Number of hops

Answer

Prefix length

Question 12

A Juniper device has multiple candidate configurations loaded. The administrator wants to discard all uncommitted changes and revert to the last committed configuration. Which command should be used?

Accepted Answer

rollback 0. The 'rollback 0' command reverts the candidate configuration to the last committed configuration, discarding all uncommitted changes. In Junos, the rollback command uses a numeric index where 0 always refers to the most recently committed configuration, effectively undoing any uncommitted edits.

Answer

delete configuration

Answer

clear configuration

Answer

load override terminal

Question 13

A network administrator is troubleshooting high latency on a link. Which command provides real-time interface statistics?

Accepted Answer

monitor interface traffic. The 'monitor interface traffic' command provides real-time, continuously updating statistics for interface traffic, including packet counts and error rates, which is essential for diagnosing high latency as it allows the administrator to observe changes in real time. Unlike static commands, this dynamic output refreshes automatically, making it ideal for troubleshooting transient issues.

Answer

show interfaces extensive

Answer

show interfaces terse

Answer

show log messages

Question 14

Which TWO statements are true about commit operations in Junos? (Choose two.)

Accepted Answer

The commit command requires the candidate configuration to be syntactically correct.. Option B is correct because the commit command validates the candidate configuration for syntax and semantic errors before merging it into the active configuration; if the candidate is not syntactically correct, the commit fails and the running configuration remains unchanged. Option C is correct because commit confirmed activates the candidate configuration on a trial basis and, if the operator does not issue a confirming commit within the default 10-minute window, Junos automatically rolls back to the previously active configuration. Option A is wrong because rollback 0 loads the last committed (active) configuration into the candidate, it does not reboot the device. Option D is wrong because commit check only validates the candidate configuration for syntax and commit-time errors without applying it to the running system. Option E is wrong because commit at schedules a configuration commit at a specified time, not a system reboot.

Answer

The rollback 0 command will cause a system reboot.

Answer

The commit check command applies the configuration to the running system.

Answer

The commit at command is used to schedule a system reboot.

Question 15

A junior administrator wants to view only the operational state of interface ge-0/0/1, including its link status and protocol state. Which command should they use?

Accepted Answer

show interfaces ge-0/0/1 terse. The 'show interfaces ge-0/0/1 terse' command displays a concise operational state of the interface, including link status (up/down) and protocol state (up/down) without configuration details. This is the standard Junos command for quickly verifying the operational status of a specific interface.

Answer

show interface ge-0/0/1

Answer

show configuration interfaces ge-0/0/1

Answer

show interfaces ge-0/0/1 extensive