Free JN0-105 Practice Test Questions and Answers (2026) | Cert Empire Practice Questions

In Juniper Networks devices, when the factory default configuration is loaded, the first step before

committing any configuration is to set up root authentication. This is crucial because it secures the

device by ensuring that only authorized users have administrative access. Without setting up a root

password, the device will not allow any commit operations, which is a safety measure to prevent

unauthorized access. This requirement emphasizes the importance Juniper places on security right

from the initial setup of the device.

One of the key advantages of Junos OS is its ability to roll back to previous configurations. This

feature allows administrators to revert to an earlier configuration state, which is invaluable for

quickly recovering from configuration errors or undesired changes. Junos OS maintains an archive of

previous configurations, enabling easy rollback to any saved state. Another significant advantage of

Junos OS is its modular design. The operating system is structured so that different processes and

services run in separate protected memory spaces, enhancing the stability and reliability of the

system. If one process fails, it does not affect the others, thereby minimizing the risk of system-wide

failures.

https://www.juniper.net/documentation/us/en/software/junos/user-access-evo/user-

access/topics/topic-map/junos-os-login-

class.html#:~:text=You%20can%20define%20any%20number,to%20an%20individual%20user%20acc

ount.

In Junos OS, each user account can be assigned only one login class. Login classes in Junos OS define

the permissions for users, controlling what they can access and modify within the system. This setup

helps in maintaining a clear and secure access control mechanism.

Reference:

Junos OS Documentation on User Accounts and Login Classes.

In Juniper firewall filter configurations, "discard" and "accept" are two valid terminating actions for a

term within a filter. The "discard" action drops the packet, preventing it from reaching its intended

destination, while the "accept" action allows the packet to pass through the filter, proceeding to its

next hop or destination. "Count" is a non-terminating action that increments a counter every time a

packet matches the term but does not inherently determine the packet's fate. "Next term" directs

the evaluation to proceed to the next term in the filter for further processing, also a non-terminating

action.

In Junos OS, when creating a new user account, the minimum required fields are the username and

the login class. The username is the identifier for the account, while the login class specifies the level

of access or permissions the user has on the device. Login classes allow for the differentiation

between various roles, such as read-only access or full administrative rights. Other information, such

as full name or user ID, is optional and not strictly necessary for the creation of a functional user

account.

When you enter ? at the command-line prompt in Junos OS, the system provides assistance in two

significant ways. Firstly, it lists the available commands and options that can be used at the current

point in the command hierarchy, aiding users in understanding what commands they can execute

next. Secondly, it displays summary information about those commands and options, providing brief

descriptions or additional context that can help users understand the function of each command or

option. This feature is particularly useful for learning the command structure or for quick reference

when specific command syntax is forgotten.

Referring to the firewall filter configuration in the exhibit, when a packet matches the specified term

limit-icmp, two actions are defined in the then statement: count count-icmp and discard. The count

count-icmp action means that each time a packet matches this term, a counter named count-icmp

will be incremented, providing a tally of how many packets have matched the term. The discard

action means that the packet will be dropped and not forwarded through the device. This effectively

prevents the packet from reaching its intended destination. There is no action specified that would

cause an ICMP destination unreachable message to be returned, nor is there any action that would

allow the packet to be forwarded.

To view real-time usage statistics for the busiest interfaces on a device running Junos OS, the correct

command is B, "monitor interface traffic." This command provides a dynamic, real-time view of the

traffic flowing through the interfaces, allowing administrators to quickly identify and monitor the

busiest interfaces on the device.

After increasing the MTU size of an interface and committing the configuration, the command to

verify the applied MTU change is D, "show interfaces ge-0/0/0." This command displays detailed

information about the interface, including the current MTU size, making it the best choice for

verifying the applied changes.

When an interface on a router is configured with an IPv4 address and is in an up state, two types of

routes are automatically created in the routing table: a local route and a direct route, making B and D

the correct answers. The local route represents the interface's IP address itself, indicating that the

router can directly receive packets addressed to this IP. The direct route represents the subnet or

network segment to which the interface is connected, indicating that the router can directly forward

packets to destinations within this subnet.

The request system configuration rescue save command in Junos OS saves the most recently

committed configuration as the rescue configuration. This rescue configuration can be used to

recover the device if future configurations cause issues. It ensures there is a stable, known-good

configuration to fall back on, which is crucial in network management and troubleshooting.

Reference:

"rescue : save configurations as the rescue: request system configuration save .................( saves the

current configs as a rescue configs )" from Useful Juniper Commands.txt​​.

Juniper official documentation: Configuring and Activating a Rescue Configuration.

The Packet Forwarding Engine (PFE) is an integral component of Juniper Networks devices,

responsible for the data plane operations. The data plane, also known as the forwarding plane, is

where the actual processing and forwarding of packets occur based on the routing and forwarding

tables. The PFE executes the forwarding decisions made by the Routing Engine (RE), handling all

packet transmissions, including routing, filtering, and switching packets towards their destination.

This contrasts with the control plane operations handled by the RE, which involve routing table

maintenance, system management, and control protocol processing.

Referring to the exhibit, the presence of the "+" symbol next to the OSPF route for 192.168.100.2/32

indicates that this is the active route being used to forward traffic. The BGP route, although present,

does not have the "+" symbol, indicating it is not the active route. In Junos OS, the routing table

displays the active route with a "+" symbol, and the fact that the OSPF route has this symbol means it

is the preferred path based on the routing protocol's decision process, which takes into account

factors such as route preference (administrative distance) and metrics.

The transport layer in the OSI model is responsible for end-to-end communication and error

recovery. In a transport header, such as TCP or UDP, the key components include the source port

number and the destination port number. These port numbers are used to identify sending and

receiving applications. The source port number indicates the port of the sending application, and the

destination port number refers to the port of the receiving application. MAC addresses, on the other

hand, are part of the data link layer (Layer 2) and would be included in an Ethernet header, not a

transport header.

In the context of VLANs (Virtual Local Area Networks) on a Juniper switch, the numerical values

assigned to each VLAN, such as those for Prod, Test, and Dev, are known as VLAN tags. These tags are

part of the 802.1Q VLAN standard, which allows multiple VLANs to coexist on a single physical

network. Each tag uniquely identifies the VLAN to which a frame belongs, enabling the switch to

segregate and manage traffic based on VLAN membership. This tagging mechanism allows for

efficient traffic separation and management, ensuring that devices within one VLAN do not receive

traffic intended for another, thus maintaining network security and efficiency.

An Ethernet frame header includes the source MAC address (B) and the destination MAC address (D).

These addresses are used to deliver the frame from one Ethernet device to another directly

connected Ethernet device on the same network segment. Ethernet frames do not include IP

addresses, as those are part of the IP packet encapsulated within the Ethernet frame.

Two physical interface properties in Junos OS include the MAC address (A) and the Maximum

Transmission Unit (MTU) size (D). The MAC address is a hardware identifier for the network interface,

while the MTU size determines the largest packet size that the interface can transmit without

needing to fragment the packet.

Routing policies in Junos OS are crucial for controlling route advertisements and path selection. The

correct answers are B and C. An import routing policy for BGP determines which received prefix

advertisements are placed in the routing information base (RIB), and policy terms are evaluated from

top to bottom, with action taken on the first match found. This sequential evaluation allows for

precise control over routing decisions.

The Packet Forwarding Engine (PFE) in Junos OS performs several key functions, including

implementing firewall filters (A) and forwarding transit traffic (C). The PFE applies firewall filter rules

to incoming and outgoing traffic and is responsible for the high-speed forwarding of packets based

on the information in the forwarding table.

MAC (Media Access Control) addresses are unique identifiers assigned to network interfaces for

communications at the data link layer of a network segment. MAC addresses are used to identify the

physical hardware on a network. In the context of Ethernet switches, the destination MAC address in

incoming frames is used to determine the appropriate output port for forwarding the frame towards

its final destination. The switch does not change the destination MAC address; it uses the MAC

address to make forwarding decisions within the local network segment.