JN0-105 Questions and Answers

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, 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.

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 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.

In a Juniper Networks device, the Packet Forwarding Engine (PFE) processes unicast traffic by forwarding it according to the existing entries in the forwarding table. When the PFE encounters unicast traffic destined for an address that has a corresponding entry in the forwarding table, it directs the traffic through a specific outgoing interface or port toward its destination. This process is based on the most efficient path determined by the routing protocols in use, ensuring that the packet reaches its intended destination through a singular path, unless specific configurations such as load balancing are in place.

Exception traffic refers to packets that the Packet Forwarding Engine (PFE) cannot process normally and must be forwarded to the Routing Engine (RE) for further processing. This includes packets destined for the router itself or packets needing special handling that the PFE cannot provide. To protect the RE from being overwhelmed by such traffic, which could potentially impact the router's control plane functions, exception traffic is rate-limited. This means that there's a threshold to how much exception traffic can be sent to the RE, ensuring that the router's critical management and control functions remain stable and responsive even during high traffic volumes or attacks.

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.

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 default configuration of a Junos device, the primary system log file is "messages" (B). This log file contains a wide range of system messages, including operational status changes, system errors, and other critical information, making it a key resource for troubleshooting and monitoring the system's health.

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.

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.

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.

When configuring the system-related settings for the current date and time on a Junos device, especially for a specific time zone like America/Los_Angeles, and the time does not automatically adjust, two effective actions can be taken. Firstly, setting the date and time manually allows for immediate correction of the system clock. This can be done via the CLI with the appropriate set date and time command. Secondly, configuring the device to use an NTP server can provide ongoing synchronization with an accurate time source, ensuring that the device maintains the correct time and date automatically in the future, even in the case of restarts or minor drifts in the internal clock.

In the scenario where the system authentication order is set to "tacplus radius password," the correct statement is (B). If the TACACS+ and RADIUS servers are unreachable or fail to respond, the system will fall back to using password authentication. This ensures that users can still authenticate using locally stored passwords if external authentication servers are unavailable.

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.

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).

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.

The Packet Forwarding Engine (PFE) in Junos OS is responsible for maintaining the forwarding table. The PFE processes incoming packets, performs route lookups in the forwarding table, and forwards packets based on this information, offloading these tasks from the Routing Engine to ensure efficient packet forwarding.

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.

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.

The OSI (Open Systems Interconnection) model is a conceptual framework used to understand network interactions in seven distinct layers. IP (Internet Protocol) addresses are part of Layer 3, known as the Network Layer. This layer is responsible for packet forwarding, including routing through intermediate routers, and it handles the logical addressing scheme of the network to ensure that packets can be routed across multiple networks and reach their destination. IP addresses provide unique identifiers for network interfaces, allowing for communication between devices on a network or across different networks.

In Junos OS, remote access to the device's CLI is commonly facilitated through Secure Shell (SSH), a protocol providing secure command-line access over an insecure network. The given exhibit indicates an attempt to set a root authentication password but does not show configuration for enabling remote access services. To enable SSH, which is not shown in the configuration snippet, you need to configure the device to accept SSH connections. This is done by enabling the SSH service within the system services hierarchy of the configuration. The correct command to add to the existing configuration for enabling remote CLI access via SSH is set system services ssh. This command activates the SSH service, allowing secure remote logins to the device.

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.

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.