Juniper JN0-105 Practice Test - Questions Answers

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.

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 Packet Forwarding Engine (PFE) in Juniper Networks devices is the heart of the data plane, handling the actual forwarding of packets based on pre-computed forwarding tables. It provides several critical services to manage and control traffic flow, including policing (to enforce bandwidth limits for certain traffic types), stateless firewall filtering (to permit or deny traffic based on predefined criteria), and Class of Service (CoS) (to prioritize traffic to ensure quality of service for critical applications). The PFE utilizes both Layer 2 (MAC addresses) and Layer 3 (IP addresses) forwarding tables to make intelligent forwarding decisions, ensuring that packets are efficiently routed toward their final destination.

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.

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, route preference (also known as administrative distance) is used to determine the preferred route among multiple routes to the same destination learned via different routing protocols. Direct and local routes, which represent directly connected networks and interfaces, typically share the same low preference value, indicating high trustworthiness because they are directly connected to the router. OSPF internal routes (routes within the same OSPF area) and OSPF AS external routes (routes that are external to the OSPF autonomous system but redistributed into OSPF) also share the same preference value, although this value is higher (indicating less trust) than for direct and local routes. This distinction helps the routing engine decide which routes to use when multiple paths are available.

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.

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.