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

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 table and forwarding table play distinct roles in a Junos OS device. The correct answers are A and D. The routing table (A) is used by the Routing Engine (RE) to select the best route among all the learned routes, while the routing table (D) stores all routes and prefixes learned from all routing protocols. The forwarding table, in contrast, contains only the active routes chosen by the RE and is used by the Packet Forwarding Engine for actual packet forwarding.

The command "monitor traffic interface ge-0/0/0" (D) initiates a packet capture on the specified interface, allowing you to view the actual packets being transmitted and received. This is useful for troubleshooting and analyzing the traffic passing through the interface in real time.

In Junos OS, when two entries for the same destination exist in the routing table, the route with the lowest preference number is selected as the active route. This preference number, also known as the route preference or administrative distance, is used to prioritize routes received from different routing protocols.

A Layer 3 router uses the destination IP address to forward packets. The correct answer is A. Routers operate at Layer 3 of the OSI model and make forwarding decisions based on IP addresses. They are responsible for routing packets across different networks by examining the destination IP address contained in the packet's header.

Operating an Interior Gateway Protocol (IGP) within an Autonomous System (AS) provides several benefits, including determining the optimal paths for data transmission (B), reacting quickly to network changes (D), and learning all about the subnets and best paths within the network (E). IGPs are designed to manage routing within a single AS efficiently, adapting to changes and ensuring data is routed through the best available paths.

In a typical network configuration, users and servers require a default gateway to communicate with devices on different networks or subnets. The default gateway is usually the router's interface on the same network, which routes the traffic to other networks. This is essential for the two users to access the remote server if the server is on a different subnet, which is indicated by the different network addresses.

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 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, as with many network operating systems, the control plane is responsible for processes that determine how to route traffic. This includes maintaining routing tables, which store information about network paths and protocols. Therefore, routing tables are indeed stored in the control plane.

Exception traffic refers to packets that cannot be processed by the normal fast-path processing of the Packet Forwarding Engine (PFE) in the forwarding plane, and thus are sent to the control plane for further processing. This might include packets destined for the router itself, packets that need to be fragmented, or packets that match certain firewall filter criteria, among other reasons.

Routing tables are not stored in the forwarding plane. However, the forwarding plane contains the forwarding table (sometimes referred to as the forwarding information base or FIB), which is a distilled version of the routing table optimized for fast packet forwarding. The forwarding plane uses this information to perform the actual transfer of packets across the network device interfaces.

When multiple users are configuring a Junos device using the "configure private" command, each user gets their own candidate configuration (C). This allows for isolated configuration sessions, where changes made by one user do not impact or interfere with the changes made by another user in their private session.

When creating a policy to accept and redistribute routes into your IGP, "route-filter" (D) is the match criteria used to identify specific route prefixes. Route filters enable you to specify which routes should be accepted, rejected, or modified based on their attributes, such as prefix length or value.

Junos OS supports several external authentication methods for administrative access, with TACACS+ (Terminal Access Controller Access-Control System Plus) and RADIUS (Remote Authentication Dial-In User Service) being among the most commonly used. Both TACACS+ and RADIUS are protocols that allow network devices to communicate with a central authentication server, enabling centralized control over user authentication and authorization. This centralization simplifies the management of user credentials and access policies, especially in larger networks with multiple devices.

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.

In a scenario where a router has a route to a specific network (in this case, 10.1.1.0/24) with a next hop that is unreachable or incorrectly specified (e.g., "r jet" seems to be a typo or an undefined entity), the router will typically discard the traffic destined for that network. This action is taken because the router cannot determine a valid path to forward the traffic. Unlike some scenarios where the router might generate an ICMP (Internet Control Message Protocol) unreachable message, in many configurations, especially in production networks, the traffic might be silently discarded without providing feedback to the sender, as generating ICMP messages for all undeliverable packets could lead to additional network congestion and potential security concerns.

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, to navigate from operational mode to configuration mode, you can use either the edit or configure command. Both commands move the CLI from operational mode, where you can view the state of the device, to configuration mode, where you can make changes to the device's configuration.

In Junos OS, when a user issues the configure exclusive command, it locks the candidate configuration for that user, preventing other users from making concurrent configuration changes. This exclusive lock ensures that configuration changes are managed in a controlled manner, reducing the risk of conflicting changes. As a result, while one user is in exclusive configuration mode, other users are prevented from entering configuration mode until the lock is released, either by the user committing the changes or exiting configuration mode.

In Juniper Networks devices, firewall filters are used to control packet flow through the device. The default action for packets that do not match any of the specified criteria in the firewall filter is to discard them, enhancing network security by ensuring that only explicitly allowed traffic can pass through. Furthermore, it is possible to configure multiple firewall filters on a device, allowing for granular control over traffic based on various criteria such as source, destination, and protocol type.

The monitor interface ge-0/0/3 command is used in Junos OS to view real-time statistics for a specific interface. This command helps in diagnosing issues like packet loss by displaying real-time updates of traffic and error statistics for the specified interface.

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.

In the Junos OS command-line interface (CLI), the keyboard shortcut Ctrl+a is used to move the cursor to the start of the line. This is a common convention in many command-line environments and text editors, providing a quick way to navigate to the beginning of the current command or line of text without having to use the arrow keys. This can be particularly useful for making quick edits to commands or for navigating long lines of text more efficiently.

If issuing the "show | compare" command in configuration mode yields no output, it indicates that there are no changes to the candidate configuration (B). This command is used to compare the current candidate configuration with the active configuration, and a lack of output suggests that the candidate configuration matches the active one, meaning no changes have been made or the changes have already been committed.

In the Junos CLI, the pipe character | is used as a filter operator to refine command output. This operator can be combined with various filtering commands like match, except, count, etc., to display only the relevant portions of the command output. For example, using | match <pattern> filters the output to show only the lines that contain the specified pattern, making it easier to find specific information within extensive command output. This functionality is especially useful in managing and troubleshooting complex configurations and network states, allowing for more efficient analysis of the device's operational status and configuration details.

In Junos OS, issuing the rollback 0 command reverts the candidate configuration to the last committed configuration. If you have made changes to some interfaces but have not committed those changes, using rollback 0 will discard these uncommitted changes, reverting to the state of the configuration at the time of the last commit. This command does not affect system files like messages.log, reboot the device, or load the factory default configuration; it simply undoes uncommitted changes.

Junos OS supports multiple login classes that can be assigned to user accounts, allowing for different levels of access and permissions. The correct answer is C, 4. These classes include "super-user," "read-only," "operator," and "unauthorized." Each class provides a different level of access to the Junos device, ranging from full configuration and operational command privileges to limited access for monitoring and viewing configurations.

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.

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.

Junos OS supports only 1 rescue configuration file on a device. This rescue configuration is a safeguard feature that allows network administrators to revert to a known good configuration in case of a configuration error or issue, ensuring network stability.