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CCNA Junos Config Basics Questions

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76
MCQmedium

Refer to the exhibit. An engineer has made changes to the candidate configuration. What will happen when the engineer issues the 'commit' command?

A.The commit will succeed but the security policy will be ignored due to a syntax error.
B.Only the interface address change will be committed because security policies require a reboot.
C.The configuration will be validated; if errors exist, the commit will fail.
D.Both the interface address and security policy will be activated.
AnswerD

Commit activates all changes in the candidate configuration.

Why this answer

Option D is correct because in Junos, the 'commit' command activates all changes in the candidate configuration atomically. Both the interface address change and the security policy will be applied simultaneously after validation. Junos does not require a reboot for security policy changes, and syntax errors cause the commit to fail, not be ignored.

Exam trap

The trap here is that candidates may think security policies require a reboot (a common misconception from other platforms) or that syntax errors are silently ignored, but Junos enforces strict validation and atomic commits.

How to eliminate wrong answers

Option A is wrong because Junos performs full syntax and semantic validation during commit; a syntax error would cause the commit to fail, not be ignored. Option B is wrong because security policies in Junos are activated immediately upon commit without requiring a reboot; only certain hardware or kernel-level changes might need a reboot. Option C is wrong because while validation does occur, if errors exist the commit fails, but the question implies no errors are present, so the commit will succeed and activate both changes.

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77
Multi-Selecteasy

Which TWO statements are true about the Junos configuration hierarchy?

Select 2 answers
A.Configuration is organized into two main hierarchies: system and interfaces.
B.The configuration is divided into a hierarchical tree.
C.Each configuration statement is terminated by a semicolon.
D.Configuration must be entered in a specific order.
E.It is a flat structure with no grouping.
AnswersB, C

Junos configuration follows a hierarchical tree structure.

Why this answer

The Junos configuration is organized as a hierarchical tree structure, where configuration statements are grouped under various hierarchy levels (e.g., 'system', 'interfaces', 'protocols'). Each statement in this tree is terminated by a semicolon, which is a fundamental syntax rule inherited from the Junos OS CLI. This hierarchical model allows for modular, structured configuration management.

Exam trap

The trap here is that candidates often assume configuration must be entered in a specific order (like Cisco IOS), but Junos allows any order because the hierarchy is defined by the structure, not the sequence of commands.

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78
Multi-Selecthard

Which TWO statements correctly describe Junos configuration hierarchy and management?

Select 2 answers
A.The 'deactivate' command permanently removes a configuration statement from the candidate.
B.The 'load merge' command imports configuration from a file and merges it with the current candidate configuration.
C.The candidate configuration is a separate copy that does not affect the active configuration until committed.
D.The 'set' command in configuration mode directly modifies the active configuration.
E.In operational mode, the 'show' command displays the candidate configuration.
AnswersB, C

'load merge' combines the file content with the existing candidate.

Why this answer

Option B is correct because the 'load merge' command in Junos imports configuration data from a file and merges it with the current candidate configuration, preserving existing statements unless explicitly overridden. This allows incremental changes without replacing the entire configuration, which is essential for efficient network operations.

Exam trap

The trap here is confusing the Junos candidate/active model with Cisco IOS's direct 'running-config' modification, leading candidates to think 'set' changes the active config or that 'deactivate' removes statements permanently.

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79
Multi-Selectmedium

Which TWO statements about the 'commit' operation in Junos are correct?

Select 2 answers
A.The commit operation validates syntax before applying, and if errors are found, the commit fails.
B.The commit operation automatically rolls back changes after 10 minutes if not confirmed.
C.The commit operation allows you to commit only a specific portion of the configuration.
D.The commit operation applies the configuration changes at the next system reboot.
E.The commit operation activates the candidate configuration as the new active configuration.
AnswersA, E

Commit includes a syntax check and fails if errors exist.

Why this answer

Option A is correct because the 'commit' operation in Junos first validates the candidate configuration for syntax errors and semantic consistency. If any errors are detected, the commit fails and the candidate configuration remains unchanged, preventing invalid configurations from being applied.

Exam trap

The trap here is confusing the standard 'commit' with 'commit confirmed', which includes a 10-minute rollback timer, and assuming that Junos allows partial commits like some other platforms (e.g., Cisco's 'commit' with 'only' option).

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80
MCQeasy

A network engineer needs to configure an interface on a Juniper device to use DHCP to obtain an IP address. Which hierarchy is used to apply this configuration?

A.set interfaces ge-0/0/0 unit 0 family inet dhcp
B.set interfaces ge-0/0/0 dhcp-client
C.set interfaces ge-0/0/0 unit 0 family inet6 dhcp
D.set interfaces ge-0/0/0 unit 0 family ppp dhcp
AnswerA

Correctly enables DHCP client on the specified interface.

Why this answer

Option A is correct because on Juniper devices, DHCP client functionality for IPv4 is configured under the `family inet` hierarchy within a logical interface unit. The command `set interfaces ge-0/0/0 unit 0 family inet dhcp` enables the interface to obtain an IPv4 address via DHCP, which is the standard method for dynamic address assignment on Ethernet interfaces.

Exam trap

The trap here is that Cisco engineers often expect DHCP client configuration to be applied directly under the physical interface (like `ip address dhcp` on Cisco IOS), but Junos requires it under the logical unit and address family hierarchy, leading candidates to choose option B.

How to eliminate wrong answers

Option B is wrong because `set interfaces ge-0/0/0 dhcp-client` is not a valid Junos configuration hierarchy; DHCP client settings must be applied under the logical unit and address family, not directly under the physical interface. Option C is wrong because `family inet6 dhcp` is used for DHCPv6 (IPv6), not for obtaining an IPv4 address via DHCP, which is the requirement in the question. Option D is wrong because `family ppp dhcp` is not a standard Junos configuration; PPP interfaces use different mechanisms (like IPCP) for address assignment, and DHCP is not applied under `family ppp`.

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81
MCQeasy

A network administrator wants to view the current candidate configuration that has not yet been committed. Which command should be used?

A.show configuration | display set
B.show configuration
C.show configuration | compare rollback 0
D.show interface terse
AnswerB

Shows the candidate configuration.

Why this answer

The command 'show configuration' displays the current candidate configuration that has been staged but not yet committed. In Junos, the candidate configuration is stored separately from the active (committed) configuration, and this command shows all uncommitted changes. Option B is correct because it directly retrieves the candidate configuration without any comparison or filtering.

Exam trap

The trap here is that candidates confuse 'show configuration' (candidate) with 'show configuration | compare rollback 0' (diff), thinking the latter shows the full candidate config, but it only shows changes, not the entire configuration.

How to eliminate wrong answers

Option A is wrong because 'show configuration | display set' displays the candidate configuration in set notation format, but the pipe to 'display set' is a formatting option, not the core command for viewing the candidate config; the base command 'show configuration' is still needed, and the question asks for the command itself, not a variant. Option C is wrong because 'show configuration | compare rollback 0' compares the candidate configuration to the most recently committed configuration (rollback 0), which shows differences rather than the full candidate configuration. Option D is wrong because 'show interface terse' displays a summary of interface status and configuration, not the candidate configuration at all.

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82
Multi-Selecthard

Which THREE statements correctly describe the behavior of the 'replace pattern' command in Junos configuration mode?

Select 3 answers
A.It validates the replacement configuration for correctness before applying.
B.It automatically commits the changes after replacement.
C.It can be used to change interface names or IP addresses throughout the configuration.
D.It operates on the candidate configuration, not the active configuration.
E.It uses regular expressions to match and replace text patterns in the configuration.
AnswersC, D, E

Common use case for bulk changes.

Why this answer

Option C is correct because the 'replace pattern' command in Junos configuration mode uses regular expressions to find and replace text strings across the entire candidate configuration, making it ideal for bulk changes such as renaming interfaces or updating IP addresses. This command operates on the candidate configuration (option D) and relies on regex patterns (option E), but it does not validate the replacement syntax (option A) nor automatically commit changes (option B).

Exam trap

The trap here is that candidates often assume 'replace pattern' performs validation or auto-commits, confusing it with other Junos commands like 'load replace' or 'commit check', when in fact it is a simple text substitution tool that requires a separate commit to take effect.

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83
MCQmedium

A network administrator wants to add a new interface configuration to the candidate configuration while preserving all existing candidate changes. Which command should be used?

A.load merge terminal
B.load replace terminal
C.load override terminal
D.load set terminal
AnswerA

Merges the new configuration with the existing candidate, preserving other changes.

Why this answer

The 'load merge terminal' command is correct because it allows you to add new interface configuration statements to the candidate configuration by entering them line by line in the terminal, merging them with any existing candidate changes without overwriting them. This preserves all previously staged modifications while incorporating the new interface settings, which is essential for incremental configuration updates in Junos.

Exam trap

The trap here is that candidates often confuse 'load merge terminal' with 'load set terminal', mistakenly thinking that 'set' commands always merge, but in Junos, 'load set terminal' replaces the entire candidate configuration with the provided set commands, similar to 'load override'.

How to eliminate wrong answers

Option B is wrong because 'load replace terminal' replaces the entire candidate configuration with the entered configuration, discarding all existing candidate changes, which does not preserve them. Option C is wrong because 'load override terminal' completely overwrites the candidate configuration with the entered configuration, removing any prior changes. Option D is wrong because 'load set terminal' expects configuration commands in 'set' format but still replaces the entire candidate configuration with the entered set commands, not merging with existing changes.

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84
MCQeasy

An administrator is configuring a static route to a remote network 10.10.10.0/24 via next-hop 192.168.1.1. Which command correctly adds this route?

A.set routing-options route 10.10.10.0/24 static next-hop 192.168.1.1
B.set routing-options static route 10.10.10.0 next-hop 192.168.1.1 mask 255.255.255.0
C.set routing-options static next-hop 192.168.1.1
D.set routing-options static route 10.10.10.0/24 next-hop 192.168.1.1
AnswerD

Correct syntax for a static route.

Why this answer

Option D is correct because the Junos syntax for configuring a static route uses the hierarchy `set routing-options static route <destination-prefix> next-hop <address>`. The prefix must include the subnet mask in CIDR notation (e.g., /24). This command installs a route to 10.10.10.0/24 with next-hop 192.168.1.1 into the routing table.

Exam trap

The trap here is that candidates familiar with Cisco IOS may try to use a separate `mask` parameter (as in Option B) or place the route directly under `routing-options route` (as in Option A), failing to recognize Junos requires the `static route` hierarchy and CIDR notation in the destination.

How to eliminate wrong answers

Option A is wrong because the hierarchy is incorrect; `route` is not a direct child of `routing-options` — static routes must be under `routing-options static route`. Option B is wrong because it incorrectly uses a separate `mask` parameter instead of CIDR notation; Junos requires the prefix length in the destination (e.g., 10.10.10.0/24), not a separate mask. Option C is wrong because it omits the destination prefix entirely; a static route must specify both the destination network and the next-hop.

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85
MCQhard

Refer to the exhibit. An engineer notices that SNMP traffic from source 10.1.1.1 is being rejected on interface ge-0/0/1. The engineer wants to allow SNMP from this source while still blocking other SNMP traffic from the 10.0.0.0/8 range. Which change should be made?

A.Add a term at the end to permit all from 10.1.1.1
B.Change the source-address in term 1 to 10.0.0.0/8 except 10.1.1.1
C.Insert a term 0 before term 1 to permit SNMP from 10.1.1.1
D.Remove the filter and apply a new filter that permits SNMP from 10.1.1.1
AnswerC

This allows specific source before blocking remainder.

Why this answer

Option C is correct because firewall filters in Junos are evaluated sequentially from the lowest term number. By inserting a new term 0 before the existing term 1 that explicitly permits SNMP traffic (UDP ports 161/162) from source 10.1.1.1, the filter will match and accept this traffic before reaching the deny term for the 10.0.0.0/8 range. This ensures the specific host is allowed while still blocking other SNMP traffic from the broader subnet.

Exam trap

The trap here is that candidates often think they can use an 'except' keyword or add a term at the end to override a previous deny, not realizing that Junos filters stop processing after the first match and do not support exclusion syntax within a source-address match.

How to eliminate wrong answers

Option A is wrong because adding a term at the end would never be evaluated if the preceding term 1 (which denies 10.0.0.0/8) already matches and rejects the traffic; Junos firewall filters stop processing after the first match. Option B is wrong because Junos does not support an 'except' modifier on source-address in a firewall filter term; you cannot exclude a single host from a prefix match within the same term. Option D is wrong because it is unnecessarily disruptive and inefficient; the existing filter can be modified by inserting a term, which is the standard Junos practice for such requirements.

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86
Drag & Dropmedium

Order the steps to configure a BGP peering session in Junos.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps
Order

Why this order

BGP requires an AS number, group configuration, and neighbor definition. Verify with 'show bgp summary'.

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87
Multi-Selecteasy

Which TWO statements about configuration storage in Junos are true?

Select 2 answers
A.The rescue configuration is stored in /config/rescue.conf.gz.
B.The rollback configurations are stored in /config/juniper.conf.0.gz, .1.gz, etc.
C.The active configuration is stored in /config/juniper.conf.gz.
D.The candidate configuration is stored in /config/.
E.The factory default configuration is stored in /etc/config/.
AnswersA, C

Rescue configuration is a special saved configuration.

Why this answer

Option A is correct because the rescue configuration is stored as a compressed file at /config/rescue.conf.gz on Junos devices. This configuration is saved using the 'request system configuration rescue save' command and can be loaded with 'rollback rescue' to recover from a configuration that prevents the device from booting properly.

Exam trap

The trap here is that candidates often confuse the numbering of rollback files (thinking .0.gz is a rollback instead of the active configuration) or assume the candidate configuration is stored persistently on disk rather than existing only in memory until committed.

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88
MCQmedium

Refer to the exhibit. The administrator has configured a default static route. However, the route does not appear in the routing table. Based on the output, what is the most likely issue?

A.The static route is not configured correctly; the prefix is missing.
B.The route is actually present and active in the routing table.
C.The route has been overwritten by a dynamic routing protocol.
D.The next-hop is unreachable because ge-0/0/0 is down.
AnswerB

The show route output confirms it is there.

Why this answer

Option B is correct because the exhibit shows the static route 0.0.0.0/0 with a next-hop of 10.0.0.1 in the routing table, indicated by the 'S' flag (static) and the active route marker '>'. The route is present and active, so the administrator's assumption that it does not appear is incorrect.

Exam trap

The trap here is that candidates may misinterpret the routing table output, thinking a static route is missing when it is actually present and active, often because they overlook the 'S' flag or the '>' indicator, or they assume the route is not shown because they expect a different format.

How to eliminate wrong answers

Option A is wrong because the static route is configured with the correct prefix 0.0.0.0/0, which is the default route, and it appears in the routing table. Option C is wrong because there is no evidence of a dynamic routing protocol overwriting the route; the static route is still present with its 'S' flag, and no other protocol's route to 0.0.0.0/0 is shown. Option D is wrong because the next-hop 10.0.0.1 is reachable via interface ge-0/0/0, which is listed as 'up' in the routing table output (the interface name appears without a 'down' indicator), and the route is active.

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89
MCQhard

An engineer needs to load a full configuration from a text file onto a Junos device, replacing the entire candidate configuration. Which command should be used?

A.load set /path/to/config.txt
B.load override /path/to/config.txt
C.load patch /path/to/config.txt
D.load merge /path/to/config.txt
AnswerB

Replaces entire candidate configuration with file contents.

Why this answer

The 'load override' command replaces the entire candidate configuration with the contents of the specified text file, discarding any existing candidate changes. This is the correct choice because the engineer explicitly needs to replace the full configuration, not merge or patch it.

Exam trap

The trap here is that candidates often confuse 'load override' with 'load merge' because both load a file, but only 'load override' discards the existing candidate configuration, while 'load merge' preserves it and can cause configuration conflicts or residual settings.

How to eliminate wrong answers

Option A is wrong because 'load set' is not a valid Junos command; the correct syntax for loading a set-based configuration is 'load set terminal' or 'load set filename', but 'load set /path/to/config.txt' is not standard and would fail. Option C is wrong because 'load patch' applies only incremental changes (diffs) to the candidate configuration, not a full replacement. Option D is wrong because 'load merge' combines the text file with the existing candidate configuration, potentially retaining old settings and not achieving a full replacement.

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90
MCQhard

Refer to the exhibit. An administrator wants to remove the address 10.0.0.2/24 from unit 0. Which configuration mode command achieves this without affecting other configuration?

A.delete interfaces ge-0/0/1 unit 0
B.delete interfaces ge-0/0/1 unit 0 family inet address
C.delete interfaces ge-0/0/1 unit 0 family inet address 10.0.0.2/24
D.delete interfaces ge-0/0/1 unit 1 family inet address 10.0.0.2/24
AnswerC

Removes only the specified address.

Why this answer

Option C is correct because the command `delete interfaces ge-0/0/1 unit 0 family inet address 10.0.0.2/24` specifically removes only the IPv4 address 10.0.0.2/24 from the logical unit 0, leaving all other configuration (such as other addresses, VLAN tagging, or protocol families) intact. In Junos, addresses are hierarchical under `family inet address`, and deleting a specific address entry does not affect sibling addresses or the unit itself.

Exam trap

The trap here is that candidates often confuse deleting the entire unit or address family with deleting a single address, leading them to choose options that remove more configuration than intended, which is a common mistake in Junos hierarchical configuration management.

How to eliminate wrong answers

Option A is wrong because `delete interfaces ge-0/0/1 unit 0` removes the entire logical unit 0, including all its addresses, protocol families, and any other configuration (e.g., VLAN ID, filters), which is too broad. Option B is wrong because `delete interfaces ge-0/0/1 unit 0 family inet address` removes all IPv4 addresses under unit 0, not just the specific 10.0.0.2/24, potentially deleting other configured addresses. Option D is wrong because it targets unit 1 instead of unit 0, so it would not affect the address on unit 0 at all; it either does nothing or modifies the wrong interface unit.

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91
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

This reads a hierarchy-format file and merges it into the candidate configuration.

Why this answer

Option D is correct because 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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92
MCQhard

While troubleshooting a routing loop, an administrator captures traffic on an interface and sees packets with TTL=1 being forwarded. This indicates a potential misconfiguration. Which command can be used to verify whether the interface is configured with 'no-ttl-propagate'?

A.show interfaces ge-0/0/0 detail
B.show configuration interfaces ge-0/0/0
C.monitor traffic interface ge-0/0/0
D.show route forwarding-table
AnswerA

Displays TTL propagate flags under the interface details.

Why this answer

The 'no-ttl-propagate' configuration is applied at the interface level to prevent TTL decrement for certain protocols like MPLS. To verify this setting, you must check the interface configuration details, which are displayed by 'show interfaces ge-0/0/0 detail'. This command shows all interface properties, including any TTL propagation settings, whereas the configuration-only view may omit operational defaults.

Exam trap

The trap here is that candidates often assume 'show configuration interfaces' will reveal all active settings, but Junos hides default or inherited parameters unless explicitly configured, making 'show interfaces detail' necessary to see operational TTL propagation behavior.

How to eliminate wrong answers

Option B is wrong because 'show configuration interfaces ge-0/0/0' displays only the explicit configuration statements; if 'no-ttl-propagate' is not explicitly configured, it will not appear, even if the default behavior is active. Option C is wrong because 'monitor traffic interface ge-0/0/0' captures live packet headers but does not display interface configuration parameters like TTL propagation settings. Option D is wrong because 'show route forwarding-table' shows the forwarding table entries and next-hop information, not interface-level protocol options such as TTL propagation.

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93
Multi-Selectmedium

Which TWO statements are true regarding the Junos OS commit model?

Select 2 answers
A.Configuration changes are activated immediately upon entering the 'set' command.
B.The 'commit check' command activates the candidate configuration if syntax is valid.
C.Multiple users can make changes simultaneously in configure private mode.
D.The 'commit confirmed' command automatically commits changes permanently.
E.The 'commit' command activates the candidate configuration.
AnswersC, E

Private mode allows multiple users to have their own candidate configurations.

Why this answer

Option C is correct because Junos OS allows multiple users to enter configure private mode, where each user has an independent candidate configuration. This prevents conflicts and allows simultaneous edits without interfering with each other's changes. Option E is correct because the 'commit' command activates the candidate configuration, making it the active configuration on the device.

Exam trap

The trap here is that candidates often confuse 'commit check' with actually activating the configuration, or assume that 'set' commands take effect immediately as in some other network operating systems like Cisco IOS, where changes are applied in real time unless using configuration sessions.

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94
Drag & Dropmedium

Order the steps to configure a VLAN on an EX Series switch running Junos.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps
Order

Why this order

VLANs are created under 'vlans' hierarchy, then interfaces are assigned as access ports. Commit and verify.

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