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Question 81:

Which Junos feature is used to provide stateful firewall protection by controlling traffic between security zones?

1. Routing policy
2. Security policy
3. CoS scheduler
4. Routing instance

Correct Answer: 2

Explanation:

Junos security policies provide stateful traffic control between security zones. They allow administrators to define which traffic is permitted or denied based on parameters such as source zone, destination zone, addresses, applications, and services. Stateful processing allows the device to track sessions and make forwarding decisions based on the state of connections. Routing policies control route information, CoS schedulers manage traffic transmission, and routing instances provide logical routing separation. Security policies are therefore a fundamental component of implementing firewall security and controlling communication between trusted and untrusted network segments.

Question 82:

Which Junos feature is used to translate private IPv4 addresses into publicly routable addresses?

1. NAT
2. STP
3. LDP
4. VRRP

Correct Answer: 1

Explanation:

Network Address Translation (NAT) translates IP addresses between different address spaces. Source NAT is commonly used to translate private IPv4 addresses into public addresses when internal users access external networks. NAT can also be used for destination translation when external users need to access internal resources. STP prevents Layer 2 loops, LDP distributes MPLS labels, and VRRP provides first-hop gateway redundancy. NAT is especially useful in IPv4 networks because private address space cannot normally be routed across the public Internet. Proper NAT configuration must account for address pools, ports, and security policies.

Question 83:

Which type of NAT provides a fixed mapping between one private address and one public address?

1. Source NAT pool
2. Static NAT
3. PAT
4. Destination port translation

Correct Answer: 2

Explanation:

Static NAT creates a permanent one-to-one mapping between an internal address and an external address. It is commonly used when an internal server must be consistently reachable through a specific public IP address. Unlike dynamic source NAT, the mapping remains fixed rather than being selected from a pool. Port Address Translation allows multiple hosts to share addresses by using different port numbers. Destination NAT can translate destination addresses for inbound traffic. Static NAT is therefore appropriate when a predictable one-to-one address relationship is required.

Question 84:

Which security concept requires administrators to grant users only the permissions necessary to perform their assigned tasks?

1. Defense in depth
2. Least privilege
3. High availability
4. Load balancing

Correct Answer: 2

Explanation:

The principle of least privilege requires users, applications, and administrators to receive only the permissions necessary to perform their intended tasks. Limiting privileges reduces the potential impact of compromised accounts, accidental configuration changes, and unauthorized activity. Defense in depth involves using multiple security controls, while high availability focuses on maintaining service availability. Load balancing distributes traffic across resources. In a Junos environment, least privilege can be supported through appropriate login classes, permissions, authentication controls, and role-based administrative access.

Question 85:

Which Junos feature can provide different administrative privileges to different classes of users?

1. Login classes
2. VLANs
3. LSPs
4. Forwarding classes

Correct Answer: 1

Explanation:

Junos login classes allow administrators to define different levels of permissions for different users. A login class can control which operational commands users can execute and which configuration areas they are allowed to access. This supports role-based administration and the principle of least privilege. For example, an operator may be permitted to view system information but not modify routing or security configuration. VLANs provide Layer 2 segmentation, LSPs provide MPLS forwarding paths, and forwarding classes are used by CoS. Login classes are therefore important for secure administrative access.

Question 86:

Which authentication method can use a centralized server to verify administrator credentials for Junos devices?

1. RADIUS
2. ARP
3. LACP
4. STP

Correct Answer: 1

Explanation:

RADIUS provides centralized authentication services for network devices and can be used to authenticate administrators connecting to Junos systems. Centralized authentication makes account management easier across multiple devices because credentials and authentication policies can be maintained on a central server. RADIUS can also provide authorization and accounting functions depending on the deployment. ARP performs IPv4 address resolution, LACP manages link aggregation, and STP prevents Layer 2 loops. Using centralized authentication can improve security and simplify administration compared with maintaining independent local accounts on every network device.

Question 87:

Which Junos feature can help protect the control plane from excessive traffic directed at the Routing Engine?

1. CoS rewrite
2. Firewall filter
3. VLAN trunking
4. Route reflector

Correct Answer: 2

Explanation:

Firewall filters can be used to control and restrict traffic destined for the Routing Engine or other protected resources, depending on the Junos platform and configuration. Protecting the control plane is important because excessive or malicious traffic can consume processing resources and affect routing protocols or management functions. Appropriate filters can limit unnecessary traffic while allowing required control and management protocols. CoS rewrite rules modify packet markings, VLAN trunking carries multiple VLANs, and route reflectors reduce iBGP session requirements. Control-plane protection should be carefully designed so legitimate routing traffic is not accidentally blocked.

Question 88:

Which protocol is commonly used to securely manage a Junos device from a remote workstation?

1. Telnet
2. FTP
3. SSH
4. TFTP

Correct Answer: 3

Explanation:

SSH provides secure encrypted remote management access to Junos devices. It protects login credentials and management sessions from being transmitted in clear text across the network. SSH is preferred over Telnet because Telnet does not provide comparable encryption. FTP and TFTP are primarily file-transfer protocols and are not intended to provide secure interactive device administration. Administrators should use secure authentication methods and appropriate access restrictions when enabling SSH. Secure management is particularly important because unauthorized access to a network device could allow attackers to modify routing, security, or interface configuration.

Question 89:

Which protocol is used by Ethernet switches to discover directly connected neighboring devices and exchange device information?

1. BGP
2. LLDP
3. OSPF
4. RADIUS

Correct Answer: 2

Explanation:

Link Layer Discovery Protocol (LLDP) allows network devices to advertise information about themselves to directly connected neighbors. Information can include system identity, port details, capabilities, and other operational information. LLDP is useful for network documentation and troubleshooting because administrators can determine which devices are connected to specific interfaces. BGP and OSPF exchange routing information, while RADIUS provides centralized authentication and authorization. LLDP operates at Layer 2 and does not require an IP routing relationship between the neighboring devices.

Question 90:

Which Ethernet switching behavior occurs when a switch does not know the destination MAC address of a frame?

1. The switch discards the frame immediately
2. The switch sends the frame only to the default gateway
3. The switch floods the frame within the appropriate VLAN
4. The switch converts the frame to an IP packet

Correct Answer: 3

Explanation:

When a switch receives a frame with an unknown destination MAC address, it generally floods the frame out appropriate forwarding ports within the same VLAN, excluding the interface on which the frame was received. This allows the destination device to receive the frame and respond, enabling the switch to learn the destination MAC address from the response. The switch does not automatically send the frame to a default gateway or convert it into an IP packet. Unknown unicast flooding is normal Layer 2 behavior, although excessive flooding can indicate a switching or topology problem.

Question 91:

Which type of Ethernet interface is normally configured to carry traffic for multiple VLANs?

1. Access interface
2. Trunk interface
3. Loopback interface
4. Management-only interface

Correct Answer: 2

Explanation:

A trunk interface carries traffic belonging to multiple VLANs across a single physical link. VLAN tags, commonly based on IEEE 802.1Q, identify the VLAN associated with each frame. Trunks are frequently used between switches, between switches and routers, or between network devices that need to transport multiple VLANs. An access interface normally carries traffic for a single VLAN. Loopback interfaces are logical Layer 3 interfaces and are not used as ordinary VLAN trunks. Proper trunk configuration is essential for maintaining VLAN connectivity across multiple switching devices.

Question 92:

Which interface type is normally assigned to an end device that belongs to a single VLAN?

1. Trunk
2. Aggregated Ethernet
3. Access
4. Loopback

Correct Answer: 3

Explanation:

An access interface is typically associated with a single VLAN and is commonly used to connect end devices such as computers, printers, or IP phones. Frames arriving from the connected device are associated with the configured VLAN without requiring the endpoint to understand VLAN trunk tagging in the normal access-port scenario. A trunk interface carries multiple VLANs, an aggregated Ethernet interface combines physical links, and a loopback interface is a logical interface used for Layer 3 purposes. Correct access-port configuration is important for ensuring endpoints are placed into the intended broadcast domain.

Question 93:

Which Junos interface type is commonly used as a stable logical address for device identification and routing protocols?

1. Loopback interface
2. Access interface
3. Trunk interface
4. Aggregated Ethernet interface

Correct Answer: 1

Explanation:

A loopback interface is a logical interface that is not tied to a specific physical network connection. Because it can remain operational as long as the device has an active path to the network, it is often used as a stable address for routing protocols, management, router identification, and other services. Loopback addresses are particularly useful in protocols such as BGP and OSPF where a stable router identifier or endpoint address is desirable. Access and trunk interfaces are physical or logical Ethernet connectivity mechanisms, while aggregated Ethernet combines multiple physical links.

Question 94:

Which BGP mechanism allows a router to advertise a default route to a BGP neighbor?

1. next-hop self
2. default-originate
3. route reflector
4. remove-private

Correct Answer: 2

Explanation:

The BGP default-originate mechanism can be used to advertise a default route to a BGP neighbor. This is useful when an organization wants downstream routers or customers to send Internet-bound traffic toward a particular upstream device. The exact conditions under which the default route is advertised can depend on the configuration and routing policy. next-hop self changes the next-hop attribute, route reflection improves iBGP scalability, and remove-private can remove private AS numbers from an AS path. Default-route advertisement should be implemented carefully to avoid unintended traffic forwarding.

Question 95:

Which Junos routing-policy action prevents a matched route from being accepted or advertised?

1. accept
2. next-hop
3. reject
4. local-preference

Correct Answer: 3

Explanation:

The reject action in a Junos routing policy prevents a matched route from being accepted or advertised, depending on where the policy is applied. Routing policies can contain match conditions and actions that determine how routes are handled. An accept action allows a matching route to proceed, while actions such as setting local preference or next hop modify route attributes. Rejecting unwanted routes is useful for controlling route exchange, reducing routing-table size, and preventing accidental advertisement of prefixes. Policies should be tested carefully before being applied to production routing sessions.

Question 96:

Which BGP attribute is commonly used to influence route selection by specifying how preferred an exit path is within an autonomous system?

1. Local preference
2. MED
3. Origin
4. Community

Correct Answer: 1

Explanation:

Local preference is a BGP attribute used to influence the preferred exit path from an autonomous system. A higher local preference is generally preferred during BGP route selection. It is propagated through iBGP and can therefore provide consistent outbound traffic engineering across routers within the same AS. MED is generally used to influence inbound path selection by a neighboring AS, while Origin indicates how a route was introduced into BGP. Communities are tags used to apply routing policies. Local preference is therefore commonly used for controlling outbound path selection.

Question 97:

Which protocol is commonly used to establish secure VPN tunnels over an IP network?

1. IPsec
2. LLDP
3. STP
4. LACP

Correct Answer: 1

Explanation:

IPsec provides security services for IP traffic and is commonly used to create encrypted VPN tunnels across untrusted networks such as the Internet. It can provide confidentiality, integrity, authentication, and anti-replay protection depending on the configured algorithms and protocols. LLDP is used for neighbor discovery, STP prevents Layer 2 loops, and LACP provides link aggregation. IPsec VPNs are frequently used to securely connect remote offices, users, or networks over public infrastructure. Correct configuration requires compatible security parameters between the participating endpoints.

Question 98:

Which security mechanism can help detect repeated failed login attempts against a network device?

1. Routing policy
2. Authentication monitoring and system logs
3. VLAN tagging
4. LDP

Correct Answer: 2

Explanation:

Authentication events and system logs can provide visibility into repeated failed login attempts. Junos logging can record authentication-related events, allowing administrators or centralized monitoring systems to identify suspicious activity. Reviewing these events can help detect password attacks, unauthorized access attempts, or misconfigured authentication clients. Routing policies manage routes, VLAN tagging identifies Layer 2 VLAN membership, and LDP distributes MPLS labels. For stronger security monitoring, device logs can be forwarded to a centralized logging or security monitoring platform where alerts and correlation rules can be applied.

Question 99:

Which Junos command can be used to display the configured routing protocols and their associated routing information?

1. show route protocol
2. show chassis hardware
3. show system uptime
4. show interfaces terse

Correct Answer: 1

Explanation:

The show route protocol command can be used to examine routes associated with a particular routing protocol, depending on the command options and Junos implementation. This is useful when troubleshooting route learning because an administrator can determine which routes were learned through OSPF, BGP, static configuration, or other sources. Hardware, uptime, and interface commands provide different categories of operational information. When a route is missing, examining the protocol-specific routes can help determine whether the problem is with route learning, policy, route selection, or installation into the forwarding table.

Question 100:

Which Junos command allows an administrator to compare the current candidate configuration with the active committed configuration before committing?

1. show route
2. show | compare
3. show interfaces terse
4. show system uptime

Correct Answer: 2

Explanation:

The show | compare command can be used in Junos configuration mode to display differences between the candidate configuration and the currently committed configuration. This is extremely useful before committing changes because it allows administrators to review exactly what will be modified. It can help identify accidental changes, missing statements, or unexpected configuration differences. The other commands provide routing, interface, or system information and do not compare configuration versions. Reviewing the output of show | compare is a good operational practice before applying significant changes to a production Junos device.