24 free Juniper JN0-106 JNCIA-Junos practice questions from the CertStash pack of 98, each with the correct answer and a full explanation. The rule is the same for every exam: ten free on the product page, 24 free here, all 98 in the pack, and each step includes the one before it.
Get all 98 questions (US$39) · Download the first 10 as a PDF
Question 1
What are two functions of the Routing Engine? (Choose two.)
Show answer and explanation
Correct answer: B, C. It runs Junos OS; It processes all management traffic.
The Routing Engine is a dedicated component in Junos devices that handles two primary functions: it runs the Junos OS operating system and it processes all management traffic destined for the device itself. Firewall filters for transit traffic and transit traffic processing are handled by the Packet Forwarding Engine (PFE), not the Routing Engine. The separation of control plane (Routing Engine) and data plane (PFE) is a core architectural principle of Junos.
Why the other options are wrong
- A. Firewall filter evaluation for transit traffic is performed by the Packet Forwarding Engine, not the Routing Engine.
- D. Transit traffic processing is a Packet Forwarding Engine function, not a Routing Engine function; the Routing Engine handles only management traffic.
Question 2
Which interface type prefix represents a 10-Gigabit Ethernet interface?
Show answer and explanation
Correct answer: B. xe
The prefix 'xe' represents 10-Gigabit Ethernet interfaces in Junos devices. Interface naming conventions in Junos use specific prefixes to denote speed and type: 'ge' for Gigabit Ethernet, 'fe' for Fast Ethernet, 'et' for 40-Gigabit Ethernet, and 'xe' for 10-Gigabit Ethernet.
Why the other options are wrong
- A. The 'ge' prefix represents Gigabit Ethernet (1 Gbps), not 10-Gigabit Ethernet.
- C. The 'et' prefix represents 40-Gigabit Ethernet, not 10-Gigabit Ethernet.
- D. The 'fe' prefix represents Fast Ethernet (100 Mbps), not 10-Gigabit Ethernet.
Question 3
Which two statements are correct regarding Layer 2 network switches? (Choose two.)
Show answer and explanation
Correct answer: A, B. Switches are susceptible to traffic loops; Switches flood broadcast traffic.
Switches operate at Layer 2 and have two key characteristics: they are susceptible to traffic loops when redundant paths exist without spanning tree protection, and they flood broadcast traffic out all ports except the incoming port. Switches do learn MAC addresses through the source MAC field of incoming frames, building a MAC address table. Switches create multiple collision domains (one per port), not a single collision domain.
Why the other options are wrong
- C. Switches actively learn MAC addresses from source addresses in received frames.
- D. Switches create one collision domain per port, not a single collision domain for all ports.
Question 4
How many usable hosts are in a /24 subnet mask?
Show answer and explanation
Correct answer: B. 254
A /24 subnet mask provides 256 total addresses (2^8). In IPv4 subnetting, the first address is the network address and the last address is the broadcast address, both unusable for host assignment. This leaves 254 usable host addresses.
Why the other options are wrong
- A. 250 is incorrect; it does not account for the proper calculation of usable addresses.
- C. 255 is the total number of usable addresses plus broadcast, not just usable hosts.
- D. 256 is the total number of addresses in a /24 subnet, but does not account for network and broadcast addresses.
Question 5
What are two fiber-optic connector types? (Choose two.)
Show answer and explanation
Correct answer: A, C. LC; SC
LC (Lucent Connector) and SC (Subscriber Connector) are both standard fiber-optic connector types widely used in networking. RJ-45 is an Ethernet copper connector, not fiber-optic. BNC is a coaxial connector used primarily for older video and some network applications, not fiber-optic.
Why the other options are wrong
- B. RJ-45 is a copper connector standard for Ethernet, not a fiber-optic connector.
- D. BNC is a coaxial connector type, not a fiber-optic connector.
Question 6
Which two characteristics apply to TCP? (Choose two.)
Show answer and explanation
Correct answer: C, D. TCP uses a three-way handshake to establish a connection; TCP provides reliable, ordered delivery using sequence numbers.
TCP establishes connections using a three-way handshake (SYN, SYN-ACK, ACK) and provides reliable, ordered delivery through sequence numbers that ensure packets arrive in order and enable retransmission of lost segments. TCP does not guarantee fixed latency; it prioritizes reliability over speed. TCP uses unicast delivery by design, not broadcast datagrams.
Why the other options are wrong
- A. TCP makes no latency guarantees; it sacrifices speed for reliability.
- B. TCP uses unicast communication between specific endpoints, not broadcast datagrams.
Question 7
You asked a network engineer to configure a new logical interface on a Juniper router. The interface must use the fourth usable host address from the 172.16.40.128/29 subnet. Which IP address is correct in this scenario?
Show answer and explanation
Correct answer: B. 172.16.40.132
The /29 subnet mask (255.255.255.248) creates 8-address blocks. The subnet 172.16.40.128/29 contains addresses 128-135. The network address is 128 and broadcast is 135, leaving usable hosts: 129 (first), 130 (second), 131 (third), and 132 (fourth). The fourth usable host address is 172.16.40.132.
Why the other options are wrong
- A. 172.16.40.135 is the broadcast address for this subnet.
- C. 172.16.40.130 is the second usable host address, not the fourth.
- D. 172.16.40.131 is the third usable host address, not the fourth.
Question 8
You are asked to subnet the broadcast domains but need to support 50 hosts. In this scenario, which subnet mask would satisfy this requirement?
Show answer and explanation
Correct answer: A. /26
To support 50 hosts, calculate the required subnet size. A /26 provides 64 total addresses with 62 usable hosts (64 - 2 for network and broadcast). A /27 provides only 32 total addresses with 30 usable hosts, which is insufficient for 50 hosts. A /28 provides 16 usable hosts, and /29 provides 6 usable hosts. Therefore, /26 is the correct choice.
Why the other options are wrong
- B. /27 provides only 30 usable host addresses, insufficient for 50 hosts.
- C. /28 provides only 14 usable host addresses, insufficient for 50 hosts.
- D. /29 provides only 6 usable host addresses, insufficient for 50 hosts.
Question 9
Which IPv4 address and subnet mask combination represents a point-to-point link with only two usable host addresses?
Show answer and explanation
Correct answer: A. 192.168.1.0/30
A /30 subnet mask provides 4 total addresses: one network address, two usable host addresses, and one broadcast address. This makes /30 the standard choice for point-to-point links such as router-to-router connections. A /29 provides 6 usable addresses (excessive), /24 provides 254 usable addresses (excessive), and /28 provides 14 usable addresses (excessive) for a point-to-point link.
Why the other options are wrong
- B. /29 provides 6 usable host addresses, more than necessary for a point-to-point link.
- C. /24 provides 254 usable host addresses, far more than needed for two hosts.
- D. /28 provides 14 usable host addresses, more than necessary for a point-to-point link.
Question 10
What is the maximum number of IP addresses that would be assigned to hosts in the 192.168.1.0/24 network?
Show answer and explanation
Correct answer: D. 254
A /24 subnet provides 256 total addresses (2^8). The first address is the network address (192.168.1.0) and the last is the broadcast address (192.168.1.255), both reserved and not assigned to hosts. This leaves 254 addresses available for host assignment.
Why the other options are wrong
- A. 24 refers to the prefix length, not the number of addresses.
- B. 32 is the total number of bits in an IPv4 address, not host count in a /24.
- C. 128 is not related to /24 subnet sizing; it represents a /25 subnet's usable count.
What people say about the full JN0-106 pack 5.0 from 6
Passed my JNCIA-Junos JN0-106 exam this morning! As someone new to Juniper, I struggled with the Junos OS CLI structure and routing policies. Cert Stash had fantastic practice questions that perfectly simulated the real exam difficulty. Thank you!
The JN0-106 exam questions helped me spot my weak areas and improve them before the exam.
The questions helped me prepare more efficiently. Free updates made me feel more confident during the study period.
Question 11
A network administrator must set up the initial configuration of the out-of-band management interface on a new Juniper router to ensure management traffic is isolated from the default routing table (inet.0). In this scenario, which configuration step is required to accomplish this task in Junos OS?
Show answer and explanation
Correct answer: D. Assign an IP address to interface fxp0.0 or em0.0 and use the command set system management-instance to enable the management routing instance.
The fxp0.0 (or em0.0 on some platforms) interface is the dedicated out-of-band management interface in Junos OS. Using the command set system management-instance creates a separate management routing instance that isolates management traffic from the default inet.0 routing table, ensuring that management traffic does not compete with data plane traffic and remains accessible even if the main routing table is unstable.
Why the other options are wrong
- A. Configuring ge-0/0/0.0 with ethernet-switching creates an in-band interface that uses the default routing table, not an isolated management path.
- B. The lo0.0 loopback interface is used for device-level addressing but does not provide true out-of-band management isolation or automatic management instance functionality.
- C. The me0.0 interface is not a standard Junos management interface, and configuring routing-options instance-type virtual-router does not establish proper management isolation.
Question 12
You successfully committed a configuration change. You now realize an issue exists and must revert back to the previous configuration. Which command entered in configuration mode will accomplish this task when committed?
Show answer and explanation
Correct answer: D. rollback 1
The rollback 1 command, when committed, reverts the router to the previous committed configuration. After a configuration has been successfully committed, rollback 1 loads the prior committed state into the candidate configuration, which is then committed to restore the previous working state.
Why the other options are wrong
- A. show | compare displays differences but does not revert configurations
- B. save config saves the current candidate configuration to a file; it does not revert to previous states
- C. rollback 0 loads the current active configuration, which is already running and not a reversion
Question 13
What are two characteristics of IPv6 addressing? (Choose two.)
Show answer and explanation
Correct answer: A, D. The IPv6 address is represented by a 128-bit address; IPv6 addresses that begin with fe80 are not routable.
IPv6 addresses are represented by 128-bit addresses, compared to IPv4's 32-bit format, allowing for a vastly larger address space. IPv6 addresses beginning with fe80 are link-local addresses, which are not routable on the internet and are used only for communication on the local network segment.
Why the other options are wrong
- B. IPv6 headers do not include a checksum; instead, checksum responsibility is delegated to upper-layer protocols and the data link layer.
- C. IPv6 uses Neighbor Discovery (ND) with ICMPv6, not ARP, to discover neighboring devices.
Question 14
What does the Junos CLI prompt indicate when it ends with a hash symbol (#)?
Show answer and explanation
Correct answer: B. The user is in configuration mode.
A hash symbol (#) at the end of the Junos CLI prompt indicates the user is in configuration mode. In operational mode, the prompt ends with a greater-than symbol (>). The hash symbol signals that configuration commands are available and changes can be made to the system configuration.
Why the other options are wrong
- A. Operational mode prompts end with a greater-than symbol (>), not a hash symbol (#).
- C. Shell mode is a separate environment accessed via the start shell command and has a different prompt format (typically $).
- D. Recovery mode is not a standard Junos CLI mode and does not use the hash symbol as a standard indicator.
Question 15
An administrator wants to set up a remote user authentication service for the many users that access a Juniper security device. In this scenario, what are two supported authentication protocols? (Choose two.)
Show answer and explanation
Correct answer: A, B. RADIUS; TACACS+
RADIUS and TACACS+ are both industry-standard protocols for remote user authentication. RADIUS uses UDP and is widely supported, while TACACS+ uses TCP and provides more detailed accounting. Both are commonly implemented for centralized authentication on Juniper security devices.
Why the other options are wrong
- C. SHA is a hashing algorithm used for data integrity and password storage, not a remote authentication protocol.
- D. IPsec is an encryption protocol for secure communications, not a user authentication service protocol.
Question 16
You power on a new MX Series router for the first time and connect to the console. You notice that no transit interfaces are passing traffic. In this scenario, which statement is correct?
Show answer and explanation
Correct answer: D. The interfaces are not configured.
On first power-on, an MX Series router has no configurations applied. Transit interfaces remain non-functional until they are explicitly configured with IP addresses, routing protocols, or other necessary parameters. The unconfigured state is the reason no transit traffic is passing through the interfaces.
Why the other options are wrong
- A. Interfaces are not automatically enabled with DHCP client configuration on initial startup.
- B. Interfaces do not automatically receive IP addresses upon power-on; configuration is required.
- C. Interfaces are not preconfigured as Layer 2 trunk ports; they must be explicitly configured for their intended role.
Question 17
What information would you find using the CLI help command?
Show answer and explanation
Correct answer: A. a URL for accessing the technical documentation
The CLI help command provides information about commands, their syntax, and typically includes references to URLs for accessing technical documentation and the full Junos documentation set. This is the standard function of the help command in the Junos CLI.
Why the other options are wrong
- B. The message of the day is displayed at login, not through the help command.
- C. Hyperlinks for remediation actions are not a function of the CLI help command.
- D. System log error message explanations are found using the request system log-message command or through documentation, not the general help command.
Question 18
Which two characteristics describe Junos OS software? (Choose two.)
Show answer and explanation
Correct answer: B, D. Junos OS supports automation features; Junos OS uses a modular architecture with independent processes.
Junos OS uses a modular architecture composed of independent processes that can be managed, updated, and restarted individually without affecting the entire system. Junos OS also supports extensive automation features including scripting, event policies, and programmable interfaces for network management and orchestration.
Why the other options are wrong
- A. Junos OS is not monolithic; it is built on a modular architecture with separate, independent processes.
- C. Junos OS runs on multiple device types including routers, switches, firewalls, and security appliances, not only routers.
Question 19
How are the Routing Engine and the Packet Forwarding Engine components connected?
Show answer and explanation
Correct answer: D. They use an internal Ethernet link.
The Routing Engine and Packet Forwarding Engine are connected through an internal Ethernet link, enabling communication between the control plane and forwarding plane within the device architecture.
Why the other options are wrong
- A. They do not use shared memory access; instead they communicate via a dedicated link.
- B. External breakout cables are not used for internal component communication.
- C. MPLS connections are not used for inter-engine communication within a single device.
Question 20
Which two statements are correct about Junos OS? (Choose two.)
Show answer and explanation
Correct answer: B, D. Junos OS provides modularization of software processes; Junos OS separates the control plane and the forwarding plane.
Junos OS provides modularization of software processes, allowing independent operation and management of different functional components. Junos OS also separates the control plane and forwarding plane, which is a fundamental architectural principle enabling independent optimization and failover capabilities.
Why the other options are wrong
- A. Junos OS does not allow execution of unsigned third-party binaries due to its security-focused design.
- C. While Junos OS supports both security and routing policies, it does not combine them; they are managed separately.
Question 21
Which command would compare the candidate configuration with the active configuration before committing the changes?
Show answer and explanation
Correct answer: A. [edit] user@router# show | compare
The show | compare command executed in configuration mode ([edit]) displays the differences between the candidate configuration and the active configuration before committing. This allows verification of intended changes.
Why the other options are wrong
- B. rollback 0 loads the active configuration into the candidate, it does not display comparisons
- C. This command is in operational mode syntax and uses incorrect filtering; show configuration | compare rollback 0 would not display candidate versus active differences properly
- D. This operational mode command syntax is incorrect for comparing candidate and active configurations
Question 22
Which two functions are performed by the PFE? (Choose two.)
Show answer and explanation
Correct answer: A, B. It processes exception traffic; It forwards incoming traffic.
The PFE (Packet Forwarding Engine) is responsible for forwarding incoming traffic at line rate and processing exception traffic (traffic that requires special handling or cannot be forwarded at line rate). The routing table and forwarding table are created by the Routing Engine, not the PFE; the PFE uses the forwarding table provided by the RE to make forwarding decisions.
Why the other options are wrong
- C. The forwarding table is created by the Routing Engine based on the routing table; the PFE only uses it for forwarding decisions.
- D. The routing table is created and maintained by the Routing Engine, not the PFE.
Question 23
Which two statements are examples of exception traffic? (Choose two.)
Show answer and explanation
Correct answer: A, B. An IP packet with the Router Alert option set in the IP options field; SSH traffic to the local Junos OS device.
Exception traffic destined for the Routing Engine includes IP packets with the Router Alert option set, which signals special handling requirements to routers. SSH traffic directed to the local Junos OS device is also exception traffic as it requires control plane processing for device management, unlike transit traffic that simply passes through.
Why the other options are wrong
- C. IP precedence bits in the ToS field affect traffic classification and QoS handling but do not inherently designate traffic as exception traffic requiring Routing Engine processing.
- D. SSH traffic to a remote server on the Internet is transit traffic forwarded by the Packet Forwarding Engine, not exception traffic.
Question 24
When troubleshooting a problem, you issue the following commands in sequence: 1. show chassis alarms 2. show chassis fpc 3. show chassis fpc detail 4. show chassis errors fpc-slot 0 In this scenario, what happens when you press the up arrow key twice at the prompt?
Show answer and explanation
Correct answer: D. The show chassis fpc detail command is displayed at the prompt.
The up arrow key cycles backward through command history. Pressing it once from the blank prompt displays the most recent command (4: show chassis errors fpc-slot 0). Pressing it a second time moves back one more position in the history, displaying command 3: show chassis fpc detail.
Why the other options are wrong
- A. The show chassis fpc command is command 2 in the sequence; pressing up twice from the end would show command 3, not command 2.
- B. The show chassis errors fpc-slot 0 command is the most recent command (4); pressing up twice moves further back in history, not to the most recent command.
- C. The show chassis alarms command is command 1; pressing up twice would only move back two positions, landing on command 3.
That was 24 of 98.
The full Juniper JN0-106 JNCIA-Junos pack has all 98 questions, each with the answer, the explanation and why the other options are wrong, plus a questions-only copy for timed runs. US$39, paid once, with free monthly updates and a pass-or-your-money-back guarantee.
Not ready yet? Get the first 33 free as one PDF by email. Get the Half Pack →