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Question 41:

Which Junos feature allows a network administrator to divide a physical switch into multiple logical Layer 2 broadcast domains?

1. VLAN
2. Routing policy
3. Routing instance
4. LSP

Correct Answer: 1

Explanation:

A VLAN, or Virtual Local Area Network, logically separates devices into different Layer 2 broadcast domains. Devices in different VLANs are isolated at Layer 2 unless routing is configured between them. VLANs are commonly used to segment users, applications, voice traffic, and management networks. Routing policies control route advertisements and attributes, while routing instances provide logical routing-table separation. An MPLS LSP provides a label-switched forwarding path and does not perform ordinary VLAN segmentation. VLAN configuration is therefore a fundamental technique for organizing and securing switched networks.

Question 42:

Which protocol is used to prevent Layer 2 switching loops by placing redundant links into a blocking state?

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

Correct Answer: 2

Explanation:

Spanning Tree Protocol (STP) prevents Layer 2 loops by calculating a loop-free topology and placing redundant paths into a blocking or non-forwarding state. Without loop prevention, redundant Ethernet links can cause broadcast storms, MAC table instability, and excessive traffic. STP allows redundant physical paths to remain available while ensuring that only appropriate paths forward traffic. LACP provides link aggregation, LLDP provides neighbor discovery, and VRRP provides first-hop gateway redundancy. STP is therefore an important Layer 2 technology for maintaining network stability when redundant switching paths exist.

Question 43:

Which VLAN tagging standard is commonly used to identify VLAN membership across a trunk link?

1. IEEE 802.1Q
2. IEEE 802.3ad
3. IEEE 802.1X
4. IEEE 802.11

Correct Answer: 1

Explanation:

IEEE 802.1Q is the standard commonly used to tag Ethernet frames with VLAN information when they traverse trunk links. The VLAN tag allows switches to identify the VLAN to which a frame belongs as it travels between network devices. Trunk interfaces can therefore carry traffic for multiple VLANs over a single physical connection. IEEE 802.3ad is associated with link aggregation, 802.1X provides port-based network access control, and 802.11 defines wireless LAN standards. Proper 802.1Q configuration is essential when carrying multiple VLANs between Junos switches.

Question 44:

Which Junos feature can provide Layer 3 routing between different VLANs?

1. STP
2. VLAN tagging
3. IRB interface
4. LACP

Correct Answer: 3

Explanation:

An Integrated Routing and Bridging (IRB) interface provides Layer 3 routing functionality for VLANs on supported Junos devices. An IRB interface can be associated with a VLAN and assigned an IP address, allowing hosts in that VLAN to communicate with other routed networks. This is commonly used for inter-VLAN routing in campus and data center environments. STP prevents Layer 2 loops, VLAN tagging identifies VLAN membership, and LACP combines multiple physical links. IRB is therefore the appropriate Junos feature when a VLAN requires a Layer 3 gateway.

Question 45:

Which protocol provides authentication and authorization for network access at the port level?

1. SNMP
2. RADIUS
3. NTP
4. Syslog

Correct Answer: 2

Explanation:

RADIUS is commonly used to provide centralized authentication, authorization, and accounting services for network access. It can be integrated with technologies such as 802.1X to authenticate users or devices before allowing network access. A centralized authentication server makes it easier to manage access policies across multiple network devices. SNMP is primarily used for monitoring and management, NTP synchronizes system time, and Syslog transports log messages. RADIUS is therefore a common choice when a network requires centralized user or device authentication and authorization.

Question 46:

Which protocol is primarily used to synchronize the clocks of network devices?

1. NTP
2. SNMP
3. FTP
4. SSH

Correct Answer: 1

Explanation:

Network Time Protocol (NTP) is used to synchronize the clocks of network devices and systems. Accurate time is important for troubleshooting, event correlation, security logging, authentication mechanisms, and operational monitoring. If devices have significantly different system times, interpreting logs and correlating events can become difficult. NTP allows devices to obtain time information from trusted time sources and maintain consistent clocks. SNMP is primarily used for monitoring, FTP transfers files, and SSH provides secure remote access. Correct NTP configuration is especially important in environments where centralized logging and security auditing are required.

Question 47:

Which security technology encrypts management traffic between an administrator and a Junos device?

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

Correct Answer: 3

Explanation:

Secure Shell (SSH) provides encrypted remote management access to Junos devices. It protects administrative sessions by encrypting authentication credentials and management traffic between the administrator and the device. SSH is therefore preferred over insecure protocols such as Telnet, where credentials and session information can potentially be transmitted without encryption. FTP and TFTP are primarily file-transfer protocols and do not provide the same secure interactive management capability. Using SSH helps protect network-device administration from interception and unauthorized observation.

Question 48:

Which Junos security feature can identify and control traffic based on predefined source and destination addresses and applications?

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

Correct Answer: 1

Explanation:

Junos security policies control traffic between security zones and can use criteria such as source zone, destination zone, source address, destination address, and application. Policies can specify actions such as permitting, denying, logging, or applying other security services. This provides granular control over traffic flows through a security device. Routing policies instead control routing information, CoS schedulers manage traffic transmission, and LDP distributes MPLS labels. Security policies are therefore a core component of implementing controlled communication between trusted and untrusted network segments.

Question 49:

Which type of NAT translates multiple private IP addresses to a shared public IP address by using different source ports?

1. Static NAT
2. Destination NAT
3. Source NAT with PAT
4. One-to-one NAT

Correct Answer: 3

Explanation:

Source NAT with Port Address Translation allows multiple private hosts to access external networks using a shared public IP address. The device differentiates sessions by translating source port information along with the source IP address. This allows many internal hosts to share a limited number of public IPv4 addresses. Static NAT generally provides a fixed one-to-one mapping, while destination NAT modifies destination information for inbound traffic. Source NAT with PAT is therefore widely used for Internet access from private IPv4 networks.

Question 50:

Which Junos command is commonly used to display the MAC address table on a switching device?

1. show ethernet-switching table
2. show ospf neighbor
3. show route
4. show bgp summary

Correct Answer: 1

Explanation:

The show ethernet-switching table command displays learned Layer 2 MAC address information on Junos switching platforms. It can show MAC addresses, VLAN associations, and the interfaces through which addresses were learned. This information is particularly useful when troubleshooting switching connectivity, unexpected flooding, or incorrect endpoint learning. show ospf neighbor displays OSPF adjacency information, show route displays routing information, and show bgp summary provides BGP peer information. Checking the Ethernet switching table is therefore an important diagnostic step when investigating Layer 2 forwarding issues.

Question 51:

Which spanning-tree protocol provides faster convergence than traditional STP by using a reduced set of port states and mechanisms?

1. RSTP
2. RIP
3. LDP
4. VRRP

Correct Answer: 1

Explanation:

Rapid Spanning Tree Protocol (RSTP) provides faster convergence than traditional Spanning Tree Protocol. It uses improved mechanisms for identifying alternate paths and transitioning ports into forwarding states more quickly after topology changes. Faster convergence reduces the amount of time during which network connectivity may be affected by a link or device failure. RIP is a routing protocol, LDP distributes MPLS labels, and VRRP provides gateway redundancy. RSTP is therefore preferred in many modern Layer 2 environments where rapid recovery from topology changes is important.

Question 52:

Which type of route is manually configured by a network administrator rather than learned dynamically from a routing protocol?

1. Connected route
2. Static route
3. BGP route
4. OSPF route

Correct Answer: 2

Explanation:

A static route is manually configured by a network administrator and does not depend on a dynamic routing protocol to learn the destination. Static routes are useful for simple networks, default routes, backup paths, or specific destinations where predictable forwarding is desired. Connected routes are automatically generated from configured interfaces, while BGP and OSPF routes are learned through their respective routing protocols. Static routing can reduce protocol overhead but may require manual changes when the topology changes. Administrators should therefore consider operational requirements before relying heavily on static routes.

Question 53:

Which route is typically used to forward traffic when no more specific route exists in the routing table?

1. Host route
2. Default route
3. Connected route
4. Loopback route

Correct Answer: 2

Explanation:

A default route provides a fallback path for destinations that do not match a more specific route in the routing table. It is commonly represented as 0.0.0.0/0 for IPv4 and ::/0 for IPv6. Enterprise networks frequently use a default route to send Internet-bound traffic toward an upstream router or service provider. A host route identifies a specific individual address, a connected route represents a directly attached network, and a loopback route represents a loopback interface. Default routes are particularly useful at network edges.

Question 54:

Which IPv6 address type is used for communication with the nearest member of a group rather than all group members?

1. Multicast
2. Anycast
3. Link-local
4. Global unicast

Correct Answer: 2

Explanation:

An IPv6 anycast address identifies a group of interfaces, with packets being delivered to the nearest interface according to the routing topology. Anycast is useful for services where clients should reach the closest available instance, such as distributed DNS or other replicated services. Multicast sends traffic to multiple members of a multicast group, while link-local addresses are used for communication within the local link. Global unicast addresses are routable IPv6 addresses intended for broader network communication. Anycast therefore provides a useful mechanism for distributed service availability.

Question 55:

Which IPv6 address type is automatically associated with an interface for communication on the local link?

1. Global unicast
2. Anycast
3. Link-local
4. Multicast

Correct Answer: 3

Explanation:

IPv6 link-local addresses are used for communication between devices on the same local link. They are typically automatically generated on IPv6-enabled interfaces and use the FE80::/10 prefix. Link-local addresses are important for IPv6 neighbor discovery and routing protocol operations. They are not intended to be routed across different network links. Global unicast addresses provide broader routability, anycast addresses identify the nearest member of a group, and multicast addresses deliver packets to multiple group members. Understanding link-local addressing is essential when troubleshooting IPv6 neighbor and routing behavior.

Question 56:

Which protocol is used by IPv6 Neighbor Discovery to resolve a neighboring device’s link-layer address?

1. ARP
2. DHCP
3. ICMPv6
4. BGP

Correct Answer: 3

Explanation:

IPv6 Neighbor Discovery uses ICMPv6 messages to perform functions that include neighbor address resolution, router discovery, and duplicate address detection. Unlike IPv4, IPv6 does not use ARP for neighbor resolution. Neighbor Solicitation and Neighbor Advertisement messages are important components of the IPv6 Neighbor Discovery process. DHCP can provide configuration information, BGP exchanges routing information, and ARP is used in IPv4 networks. Understanding ICMPv6 is therefore important when troubleshooting IPv6 connectivity, especially issues involving neighbor discovery and local-link communication.

Question 57:

Which Junos routing table is typically used to store active routes selected for forwarding?

1. inet.0
2. inet6.0
3. mpls.0
4. ethernet-switching.0

Correct Answer: 1

Explanation:

The inet.0 routing table is the primary IPv4 unicast routing table in Junos. It contains active IPv4 routes selected for forwarding, including routes learned from protocols such as OSPF, BGP, and static configuration. IPv6 unicast routes are generally stored in inet6.0, while MPLS-related forwarding information is associated with MPLS tables such as mpls.0. Ethernet switching uses different Layer 2 forwarding structures. Knowing the appropriate Junos routing table helps administrators diagnose whether routes are being learned and installed as expected.

Question 58:

Which Junos command can be used to test whether a destination is reachable using ICMP?

1. traceroute
2. ping
3. telnet
4. monitor traffic

Correct Answer: 2

Explanation:

The ping command uses ICMP echo requests and replies to test basic IP connectivity between the local device and a destination. It can help determine whether a destination is reachable and can provide information about packet loss and round-trip time. traceroute is used to discover the path packets take toward a destination, while telnet can test TCP connectivity to a particular port. monitor traffic is used for packet-level observation and troubleshooting. Ping is therefore usually one of the first tools used when checking basic network reachability.

Question 59:

Which troubleshooting command can identify the Layer 3 hops taken toward a destination?

1. ping
2. show interfaces terse
3. traceroute
4. show ethernet-switching table

Correct Answer: 3

Explanation:

The traceroute command helps identify the Layer 3 path packets take toward a destination by displaying intermediate routing hops. It is particularly useful when connectivity exists but traffic is taking an unexpected path or failing somewhere between the source and destination. Ping can confirm reachability and measure response time but does not normally show each intermediate router. Interface and switching-table commands provide local device information rather than the routed path. Traceroute is therefore an important diagnostic tool for identifying where along a routed path connectivity problems may occur.

Question 60:

Which Junos configuration mode is used to make and commit configuration changes?

1. Operational mode
2. Configuration mode
3. Shell mode
4. Diagnostic mode

Correct Answer: 2

Explanation:

Junos configuration mode is used to create, modify, delete, and commit device configuration statements. Administrators enter configuration mode using the configure command from operational mode. Changes are initially made to the candidate configuration and become active after a successful commit. Operational mode is primarily used to monitor and troubleshoot the device, while shell access provides an underlying operating-system environment and should be used carefully. The separation between operational and configuration modes is a key characteristic of Junos and helps administrators safely manage network-device changes.