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Question 141

Which protocol establishes encrypted tunnels between network endpoints?

1. IPsec
2. VRRP
3. OSPF
4. LLDP

Correct Answer: 1

Explanation:

IPsec provides security mechanisms for protecting IP communication between network endpoints. Depending on the configured architecture, IPsec can authenticate peers, protect packet integrity, and encrypt traffic traveling through an untrusted network. It is commonly used in site-to-site VPNs and other secure tunneling designs. VRRP provides gateway redundancy, OSPF exchanges internal routing information, and LLDP discovers directly connected devices. Therefore, IPsec is the correct answer because it provides cryptographic protection for IP traffic between participating endpoints. Its security capabilities make it a fundamental technology for building protected VPN connections over public or shared networks.

Question 142

Which protocol provides loop-free Layer 2 topology using multiple instances?

1. RSTP
2. MSTP
3. VRRP
4. LACP

Correct Answer: 2

Explanation:

Multiple Spanning Tree Protocol, or MSTP, allows multiple VLANs to be mapped into different spanning-tree instances. This provides a way to manage Layer 2 topology while avoiding loops and distributing traffic across available redundant paths. Instead of requiring a completely separate spanning-tree process for every VLAN, MSTP can group VLANs into instances and apply topology decisions to those groups. RSTP provides rapid convergence but does not provide the same multiple-instance structure, while VRRP handles gateway redundancy and LACP combines links. Therefore, MSTP is the correct answer because it provides multiple spanning-tree instances for Layer 2 networks.

Question 143

Which routing protocol uses hop count as its primary metric?

1. IS-IS
2. RIP
3. BGP
4. OSPF

Correct Answer: 2

Explanation:

Routing Information Protocol, or RIP, uses hop count as its primary routing metric. Each router traversed toward a destination contributes a hop, and paths with fewer hops are generally preferred within RIP’s routing process. RIP also has a relatively small maximum hop-count range, which limits its usefulness in larger modern networks. IS-IS and OSPF use link-state calculations with more sophisticated metrics, while BGP relies on path attributes and policy-based selection. Therefore, RIP is the correct answer because hop count is its defining routing metric for comparing available routes.

Question 144

Which technology provides virtual Layer 2 services over MPLS?

1. VPLS
2. VRRP
3. IPsec
4. DHCP

Correct Answer: 1

Explanation:

Virtual Private LAN Service, or VPLS, provides a Layer 2 VPN service over an MPLS provider network. It allows geographically separated customer Ethernet sites to appear as though they are connected to a common Layer 2 broadcast domain. The provider network transports customer Ethernet frames through pseudowire-based mechanisms while keeping the service separated from other customers. VRRP provides gateway redundancy, IPsec protects IP traffic, and DHCP provides host configuration. Therefore, VPLS is the correct answer because it specifically delivers virtual Ethernet connectivity across an MPLS-based provider infrastructure.

Question 145

Which mechanism identifies traffic using differentiated service markings?

1. DSCP
2. ARP
3. BFD
4. DNS

Correct Answer: 1

Explanation:

Differentiated Services Code Point, or DSCP, is used to classify IP packets according to their intended forwarding treatment. The DSCP value is carried within the IP header and can be examined by network devices to apply different queuing, scheduling, congestion-management, or forwarding policies. This makes DSCP useful for implementing Quality of Service strategies across routed networks. ARP resolves IPv4 addresses to hardware addresses, BFD detects forwarding failures, and DNS provides name resolution. Therefore, DSCP is the correct answer because it provides a standardized field for identifying traffic classes and differentiated forwarding requirements.

Question 146

Which protocol distributes labels for MPLS forwarding entries?

1. LDP
2. DHCP
3. RADIUS
4. NTP

Correct Answer: 1

Explanation:

Label Distribution Protocol, or LDP, distributes MPLS labels between participating routers so that label-switched paths can be established based on forwarding equivalence classes. LDP communicates label bindings and allows routers to build the necessary label-forwarding information for MPLS traffic. It is commonly used when MPLS forwarding follows the underlying IP routing topology rather than requiring explicit traffic-engineered paths. DHCP provides host configuration, RADIUS supports centralized authentication, and NTP synchronizes clocks. Therefore, LDP is the correct answer because it specifically distributes label information required for MPLS forwarding.

Question 147

Which technology separates traffic into logical broadcast domains?

1. VLAN
2. GRE
3. IPsec
4. RSVP

Correct Answer: 1

Explanation:

A Virtual Local Area Network, or VLAN, logically separates Ethernet traffic into distinct broadcast domains. Devices assigned to different VLANs can remain isolated at Layer 2 even when they share the same physical switching infrastructure. Communication between separate VLANs generally requires Layer 3 routing or another appropriate inter-VLAN mechanism. GRE provides tunneling, IPsec provides secure IP communication, and RSVP provides signaling for resource or traffic-engineering functions. Therefore, VLAN is the correct answer because its primary purpose is creating separate logical Layer 2 broadcast domains within a shared switching environment.

Question 148

Which protocol transports routing information using TCP connections?

1. BGP
2. OSPF
3. RIP
4. IS-IS

Correct Answer: 1

Explanation:

BGP uses TCP as its transport protocol for exchanging routing information between BGP speakers. TCP provides reliable, ordered delivery for BGP messages and maintains a session between neighboring speakers. BGP sessions use TCP port 179. OSPF operates directly over IP rather than using TCP, RIP commonly uses UDP, and IS-IS operates directly at the data-link layer rather than relying on TCP. Therefore, BGP is the correct answer because its routing-information exchange depends on persistent TCP sessions between configured peers.

Question 149

Which protocol discovers IPv6 routers on local links?

1. NDP
2. FTP
3. LACP
4. GRE

Correct Answer: 1

Explanation:

IPv6 Neighbor Discovery Protocol, commonly abbreviated NDP, provides several local-link discovery functions, including router discovery. IPv6 hosts can receive Router Advertisement messages containing information about available routers, prefixes, and other network parameters. This allows hosts to identify suitable default routers and learn information needed for IPv6 configuration. FTP provides file transfer, LACP manages link aggregation, and GRE provides generic tunneling. Therefore, NDP is the correct answer because IPv6 router discovery is one of its fundamental functions. NDP is implemented through ICMPv6 messaging and replaces several IPv4-era discovery mechanisms.

Question 150

Which Junos command displays interface addresses and operational states?

1. show interfaces terse
2. show route terse
3. show chassis alarms
4. show system storage

Correct Answer: 1

Explanation:

The Junos show interfaces terse command provides a concise summary of interfaces, including interface names, administrative states, operational states, and configured addresses where applicable. It is particularly useful when administrators need a quick overview of the device’s interface status without reviewing the extensive details provided by more comprehensive interface commands. show route terse focuses on routing entries, show chassis alarms displays hardware-related alarms, and show system storage provides storage information. Therefore, show interfaces terse is the correct answer because it gives a compact operational overview of network interfaces and their addressing information.

Question 151

Which technology provides redundant gateways using one virtual address?

1. VRRP
2. VXLAN
3. LDP
4. Syslog

Correct Answer: 1

Explanation:

VRRP allows multiple routers to participate in a virtual-router arrangement that presents a shared virtual IP address to connected hosts. One router performs the forwarding role while another participating router can assume that role when required. This means hosts can continue using the same default-gateway address even when the active physical router changes. VXLAN provides network overlays, LDP distributes MPLS labels, and Syslog records system events. Therefore, VRRP is the correct answer because it provides default-gateway redundancy through a shared virtual address.

Question 152

Which routing protocol supports hierarchical area-based network design?

1. OSPF
2. RIP
3. BGP
4. PIM

Correct Answer: 1

Explanation:

OSPF supports hierarchical network design through the use of areas. A multi-area OSPF architecture can divide a larger routing domain into smaller logical sections, reducing the amount of topology information that must be maintained by every router. Area 0 functions as the backbone and provides connectivity between non-backbone areas according to OSPF design rules. RIP does not provide an equivalent area hierarchy, BGP uses autonomous-system and policy concepts, and PIM handles multicast forwarding. Therefore, OSPF is the correct answer because its area architecture supports hierarchical internal routing designs.

Question 153

Which protocol provides centralized device configuration and monitoring data?

1. NETCONF
2. ARP
3. PIM
4. STP

Correct Answer: 1

Explanation:

NETCONF is a network-management protocol designed for retrieving and manipulating structured device configuration and state information. It commonly works with structured data models and can support transactional configuration operations, making it useful for automation and centralized network management. Administrators and management systems can use NETCONF to interact programmatically with supported network devices rather than relying exclusively on interactive CLI sessions. ARP handles address resolution, PIM handles multicast routing, and STP prevents Layer 2 loops. Therefore, NETCONF is the correct answer because it provides a standardized mechanism for programmatic configuration and operational-data management.

Question 154

Which encapsulation carries IPv6 traffic inside IPv4 packets?

1. 6in4
2. VLAN
3. PPP
4. MPLS

Correct Answer: 1

Explanation:

6in4 is a tunneling technique that encapsulates IPv6 packets within IPv4 packets. It allows IPv6 traffic to traverse an IPv4 infrastructure when native IPv6 forwarding is unavailable along part of the path. The IPv4 network acts as the transport underlay while the encapsulated IPv6 packet is carried between configured tunnel endpoints. VLAN provides Layer 2 segmentation, PPP supports point-to-point communication, and MPLS uses labels for forwarding. Therefore, 6in4 is the correct answer because its specific purpose is transporting IPv6 packets through an IPv4 network using tunneling.

Question 155

Which mechanism marks packets for Quality of Service handling?

1. DSCP
2. LLDP
3. ARP
4. DHCP

Correct Answer: 1

Explanation:

DSCP values allow IP packets to be marked according to their desired Quality of Service treatment. Network devices can inspect these markings and place packets into different forwarding classes or apply different scheduling and congestion-management behaviors. This enables administrators to distinguish traffic types such as latency-sensitive applications from ordinary data flows. LLDP identifies neighboring devices, ARP resolves IPv4 addresses, and DHCP supplies host configuration. Therefore, DSCP is the correct answer because it provides packet-level markings that can be used by network devices to implement differentiated Quality of Service treatment.

Question 156

Which Junos feature safely tests configuration changes before commitment?

1. commit confirmed
2. commit synchronize
3. load override
4. rollback rescue

Correct Answer: 1

Explanation:

The Junos commit confirmed feature allows administrators to activate configuration changes temporarily while requiring confirmation within a specified period. If confirmation does not occur before the timer expires, the device can automatically revert to the previous committed configuration. This is particularly useful when making remote changes that could accidentally disrupt management connectivity. The feature provides a safety mechanism because an administrator can test the new configuration before permanently accepting it. The other commands serve different configuration-management purposes. Therefore, commit confirmed is the correct answer for safely testing potentially disruptive configuration changes.

Question 157

Which protocol advertises network prefixes between autonomous systems?

1. BGP
2. LLDP
3. NTP
4. LACP

Correct Answer: 1

Explanation:

BGP is the principal routing protocol used to exchange network reachability information between autonomous systems. It advertises prefixes along with attributes that help receiving routers evaluate and apply routing policies to those routes. This interdomain role distinguishes BGP from protocols primarily designed for internal routing or device discovery. LLDP discovers neighboring devices, NTP synchronizes clocks, and LACP manages aggregated Ethernet links. Therefore, BGP is the correct answer because it is designed to exchange reachable network prefixes between autonomous systems and apply policy-driven path selection to those advertisements.

Question 158

Which VPN service connects Layer 3 customer sites?

1. L3VPN
2. VPLS
3. VLAN
4. STP

Correct Answer: 1

Explanation:

A Layer 3 VPN, commonly called an L3VPN, provides routed connectivity between customer sites across a provider network. The provider maintains separate customer routing information and forwards traffic according to the appropriate VPN context. This allows multiple customers to share provider infrastructure while keeping their Layer 3 routing information logically separated. VPLS provides Layer 2 VPN connectivity, VLAN provides local Layer 2 segmentation, and STP prevents switching loops. Therefore, L3VPN is the correct answer because it specifically provides routed VPN connectivity between geographically separated customer networks.

Question 159

Which protocol provides neighbor reachability detection for IPv6?

1. NDP
2. RADIUS
3. DHCP
4. GRE

Correct Answer: 1

Explanation:

IPv6 Neighbor Discovery includes Neighbor Unreachability Detection, which allows an IPv6 node to determine whether a neighboring device remains reachable. The mechanism uses ICMPv6 Neighbor Solicitation and Neighbor Advertisement messages together with information learned through normal communication. This helps devices maintain accurate information about neighboring nodes and detect when a previously reachable neighbor is no longer responding. RADIUS provides centralized authentication, DHCP provides configuration services, and GRE provides tunneling. Therefore, NDP is the correct answer because IPv6 neighbor reachability detection is an integral part of its Neighbor Discovery functionality.

Question 160

Which mechanism bundles several physical interfaces into one logical interface?

1. LAG
2. VLAN
3. VRF
4. GRE

Correct Answer: 1

Explanation:

A Link Aggregation Group, or LAG, combines multiple physical Ethernet interfaces into one logical connection. This arrangement can increase aggregate bandwidth and provide redundancy because traffic can use multiple member links. Network devices treat the group as a logical interface while internally distributing traffic across its physical members according to configured forwarding behavior. VLAN creates logical broadcast domains, VRF separates routing instances, and GRE provides packet tunneling. Therefore, LAG is the correct answer because its purpose is to combine multiple physical links into a single logical connectivity construct.