Juniper JN0-105 Junos - Associate (JNCIA-Junos) 2025 Exam Exam Practice Test

In the given telnet command, "telnet 10.10.10.1 source 192.168.100.1," the destination address of the telnet session is 10.10.10.1, and the source address of the session is specified as 192.168.100.1, making C and D the correct answers. This command instructs the telnet client to use the specified source IP address when establishing the connection to the destination.

The Routing Engine (RE) in Junos OS has several critical functions, including processing all management traffic (A) and running the Junos operating system (B). The RE handles system management tasks, user interfaces, system services, and routing protocol processes. It does not directly process transit traffic or evaluate firewall filters for transit traffic, as these tasks are handled by the Packet Forwarding Engine (PFE).

In Junos OS, the archival configuration under [edit system] allows for the automatic backup of configuration files to designated locations upon commit. When multiple archive-sites are specified, as shown in the exhibit with both SCP and FTP sites listed, the device does not choose between them or use them in a round-robin manner. Instead, it attempts to transfer the configuration backup files to all specified sites simultaneously upon each commit. This ensures redundancy and increases the likelihood that a backup will be successfully stored even if one of the transfer methods or destinations fails.

At the operational mode prompt on a Junos device, you can use various commands to view the device's status and request system operations. The show interface ge-0/0/0 command is used to display information about a specific interface, while the request system shutdown command is used to properly shut down the device. The set command is used in configuration mode, not operational mode, and the run command is used to execute operational mode commands from configuration mode.

The candidate configuration in Junos OS is a temporary configuration that allows network administrators to make and stage multiple configuration changes before applying them to the device. This approach enables the deployment of multiple changes in a single operation, ensuring that all configurations work together as intended before making them active. Additionally, the candidate configuration can be discarded if the administrator decides not to apply the staged changes, allowing for a "trial and error" approach without affecting the currently active configuration. This feature provides flexibility and reduces the risk of disruptive changes to the network.

In Junos OS, the management daemon (mgd) is responsible for handling all the device management tasks, including processing CLI commands and handling commit operations. The mgd daemon interacts with the Junos OS configuration database and provides the necessary logic to ensure that configuration changes are syntactically correct and do not conflict with each other. When a user commits a configuration, mgd validates the changes, applies them to the running configuration, and ensures that the necessary daemons are notified of the changes to apply them accordingly.

RADIUS, which stands for Remote Authentication Dial-In User Service, provides authentication services for users trying to access a network. It is a networking protocol that provides centralized Authentication, Authorization, and Accounting (AAA) management for users who connect and use a network service.

Layer 2 network switches are crucial components in local area networks (LANs), providing multiple functions for data packet forwarding and network segmentation. One inherent characteristic of switches is their susceptibility to traffic loops, especially in networks with redundant paths. Without proper loop prevention protocols like Spanning Tree Protocol (STP), loops can cause broadcast storms and network instability. Additionally, switches inherently flood broadcast traffic to all ports within the broadcast domain, except the port on which the broadcast was received. This is because broadcast frames are meant to be delivered to all devices within the VLAN, and the switch ensures this by flooding these frames to all ports in the VLAN, except the source port.

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.

In the OSI model, the Data Link Layer is responsible for node-to-node delivery of data. It frames the packets received from the Network Layer and prepares them for physical transmission. The Protocol Data Unit (PDU) for the Data Link Layer is called a "frame." Frames encapsulate the network layer packets, adding a header and a trailer that include the hardware addresses of the source and destination, among other things, facilitating the data link layer services like frame synchronization, flow control, and error checking.

For the users in the 10.1.1.0/24 subnet and the server in the 10.1.2.0/24 subnet to communicate with each other, they need to route packets through the router that connects these two subnets. Each user and the server need to have their default gateway set to the IP address of the router interface on their respective subnet (.254). This ensures that packets destined for other subnets are sent to the router, which then routes them to the correct destination subnet.

References:

Juniper official documentation: Configuring Basic Routing.

General networking principles.

Junos OS supports multiple methods for automatically archiving configurations upon commit. Two of the supported methods are SCP (Secure Copy Protocol) and RCP (Remote Copy Protocol). These methods can be configured to save the configuration files to a remote server automatically whenever a commit is made.

To recover the root password on a Junos router without losing the configuration, you should (A) enter and commit the new root password once you have gained access to the system, (D) hit the space bar to interrupt the boot process and enter recovery mode when prompted during the boot process, and (E) use a console connection to reboot the device and access the bootloader prompt. These steps allow you to reset the root password while preserving the existing configuration.

The Address Resolution Protocol (ARP) is responsible for mapping an IPv4 address to a machine's MAC address. ARP operates at Layer 2 of the OSI model and is used to find the MAC address of a host given its IPv4 address. When a device wants to communicate with another device on the same local network, it uses ARP to discover the recipient's MAC address.

References:

Juniper official documentation: ARP.

Networking standards: RFC 826.

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.

The forwarding table in a network device requires specific information to efficiently forward traffic toward its destination. This includes the next hop IP address, which indicates the next router or device in the path to the destination. The outgoing interface name identifies the physical or logical interface through which the packet should be sent to reach the next hop. Lastly, the next hop MAC address is crucial for Layer 2 forwarding decisions, allowing the device to encapsulate the IP packet in a frame that can be understood by Ethernet or other Layer 2 protocols. OSPF metric values and BGP local preference values are used in the routing decision process to select the best path and populate the forwarding table but are not directly used by the forwarding table to forward traffic.

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%20account.

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.

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.

The exhibit shows a ping test being executed from router R2 to the IP address 10.23.0.3. Since the ping command is issued on R2 and we see successful replies from 10.23.0.3, it means the source of the ping must be an interface on R2. Given the network diagram and the IP address scheme, the source IP address of the ping is on the interface ge-0/0/2 of R2, which is in the subnet 10.23.0.0/24. The only logical IP address for R2's interface in this subnet, based on standard networking practices and the given options, would be 10.23.0.2. The other addresses provided in the options belong to different subnets or are the destination of the ping itself.

The firewall filter configuration in the exhibit specifies a filter with two terms. Term 1 matches traffic from the source address 10.0.0.0/8 and has two actions: 'log' and 'next term'. The 'log' action will record the match to a log file, and 'next term' indicates that the firewall should evaluate the next term after logging. There is no explicit action such as 'accept' or 'reject' in term 1, so by default, the traffic will be accepted unless subsequently rejected by another term.

Term 2 has the action 'reject', which discards packets that reach this term. Since there is no 'from' condition in term 2, it acts as a default rule for all traffic not matched by term 1.

Because the traffic sourced from 10.0.0.0/8 matches term 1 and there is no reject action in that term, it will be logged and then accepted by the firewall filter. There is no subsequent term that rejects this specific traffic, so the action from term 2 does not apply to it.

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.

Implementing Class of Service (CoS) in a network provides numerous benefits, particularly in managing traffic based on its importance, source, or type. CoS enables network administrators to manage traffic congestion by applying various queuing techniques and policies to ensure that critical services remain unaffected during high congestion periods. Additionally, CoS allows for the prioritization of latency-sensitive traffic such as voice and video, ensuring that these services maintain quality despite varying network conditions.

The Routing Protocol Daemon (rpd) in Junos OS is responsible for maintaining routing protocols and tables. It handles all routing information, including the calculation of routes and the population of the routing table, making it crucial for dynamic routing operations.

To advertise a default static route into OSPF on router R1, a routing policy should be configured. This policy would typically include a statement to match the default route (0.0.0.0/0) and then apply an action to set the route as an OSPF external type, which would then be redistributed into the OSPF domain. The routing policy is a set of conditions and actions that determine how routes are imported into or exported from the routing table and how routes are shared between routing instances or routing protocols. After defining the policy, it must be applied to OSPF under the export section of the OSPF configuration on R1. This process will allow R1 to announce the default route to other OSPF routers in the network, which then can use it as a gateway of last resort to reach the Internet or other networks not explicitly known to the OSPF domain.

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.

UDP (User Datagram Protocol) is known for being connectionless (D) and providing best-effort delivery without the reliability mechanisms present in TCP (C). This means that UDP does not establish a connection before sending data and does not guarantee delivery, order, or error checking, making it faster but less reliable than TCP.

In Junos OS, the ? command modifier is used to display all possible completions for a specific command. This helps users understand the available options and syntax for a command they are trying to use.

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.

In Junos OS, the request system configuration rescue save command is used to save the current active configuration as a rescue configuration. This feature is particularly useful for preserving a known good configuration state that can be quickly reverted to in case of configuration errors or issues. By saving a rescue configuration, administrators can ensure that they have a reliable fallback option that can be loaded in the future to restore the device's operation without having to reconfigure from scratch. This is an essential practice for maintaining network stability and quick recovery.

In Junos OS, the prompt employee@R1> indicates the current context of the user interface. The 'R1' part of the prompt signifies the hostname of the device, which in this case is 'R1'. The absence of a '#' symbol at the end of the prompt suggests that the user is in operational mode, as opposed to configuration mode which is indicated by a prompt ending in '#'. Operational mode allows users to view the status of the device and execute operational commands, but does not allow for configuration changes.