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

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.

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.

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.

To convert the decimal number 7 to binary, the correct representation is 00000111 (C). In binary, 7 is represented as 1+2+4 (2^0 + 2^1 + 2^2), which corresponds to the last three digits being 1 in the binary format, with leading zeros added for clarity.

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.

Junos OS can store up to 50 rollback configuration files, making B the correct answer. These rollback files allow administrators to revert to previous configurations, providing a safety net that facilitates recovery from configuration errors or undesired changes

If you've committed a configuration and then need to revert to the previous configuration, the rollback command is used. Since the incorrect IP address has not been committed, as indicated by the commit check command being successful, issuing rollback 1 will undo the changes made in the current session, which includes the accidental entry of the IP address.

Transit traffic that traverses the forwarding plane of a Layer 3 router includes both unicast and multicast traffic types. Unicast traffic is directed from a single source to a single destination, while multicast traffic is sent from one source to multiple destinations that are part of a multicast group. These types of traffic are efficiently routed through the network by leveraging the router's forwarding plane capabilities. Exception traffic, which requires special handling by the control plane, and broadcast traffic, which is typically limited to a single broadcast domain and not usually forwarded by Layer 3 routers, are not considered standard types of transit traffic for the forwarding plane of a router.

Exception traffic includes traffic that is not simply forwarded by the router but requires special handling, such as routing updates (B) and log messages (C). These types of traffic are processed by the router's control plane rather than just being forwarded through the data plane.

In Junos OS routing policy evaluation, "next policy" (A) and "next term" (C) are common actions that affect the flow of policy evaluation. "Next policy" directs the evaluation to the next policy in the sequence, whereas "next term" moves the evaluation to the next term within the current policy, allowing for granular control over routing decisions.

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.

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.

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.

In Junos OS, a policer is a feature used to limit the rate of traffic flow in the network, including exception traffic sent from the Packet Forwarding Engine (PFE) to the Routing Engine (RE). Exception traffic consists of packets that cannot be processed by the PFE alone and require intervention by the RE, such as control packets or packets destined for the device itself. A policer can be configured to enforce bandwidth limits and drop or mark packets that exceed specified rate limits, thus protecting the RE from being overwhelmed by excessive exception traffic.

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.

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.

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.

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.

The show chassis hardware command in Junos OS displays detailed information about the hardware installed in the device, including the chassis itself. This command provides a list of all hardware components, their serial numbers, part numbers, and version information. When looking for the chassis serial number specifically, this command is the most direct and comprehensive way to retrieve that information, as it includes the serial number of the chassis among the details provided.

The "request system configuration rescue save" command in Junos OS saves the most recently committed configuration as the rescue configuration, making A the correct answer. This feature allows administrators to set a known good configuration that can be quickly reverted to in case of configuration errors or issues.

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 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.

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 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.

Link-state routing protocols are a type of routing protocol used in packet-switching networks for finding the best path between source and destination. OSPF (Open Shortest Path First) and IS-IS (Intermediate System to Intermediate System) are both examples of link-state routing protocols. They work by maintaining a complete map or topology of the network, allowing routers to independently calculate the best path to each destination. Unlike distance-vector protocols like RIP, link-state protocols are more efficient and scalable, making them suitable for larger networks.

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 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.

The request system zeroize media command on a Junos device securely erases all data, including configuration and log files, and resets the device to its factory default settings. This command is used when redeploying a device to ensure no residual data remains from its previous deployment. It's a comprehensive and secure way to clear all configurations and data, making the device as if it were new. The other commands listed do not perform a full reset to factory defaults; for example, show system storage displays storage information, and request system storage cleanup offers to delete unnecessary files without resetting the device to factory settings.