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Question 121

Which protocol provides gateway redundancy for connected hosts?

1. VRRP
2. PIM
3. RSVP
4. GRE

Correct Answer: 1

Explanation:

Virtual Router Redundancy Protocol, or VRRP, provides first-hop gateway redundancy for hosts on an IP network. Multiple routers can participate in a virtual-router arrangement, while one device performs the active forwarding role and another can take over when necessary. Hosts use the virtual IP address as their default gateway rather than depending directly on one physical router address. This design helps maintain gateway availability when a participating router becomes unavailable. PIM handles multicast routing, RSVP can support resource reservation and traffic-engineering functions, and GRE provides tunneling. Therefore, VRRP is the correct answer for gateway redundancy.

Question 122

Which protocol transports Ethernet frames through IP networks?

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

Correct Answer: 3

Explanation:

Ethernet VPN, or EVPN, provides a control-plane framework for extending Layer 2 connectivity across IP or MPLS-based networks. It allows Ethernet services to be represented and advertised using BGP, supporting scalable data-center and service-provider architectures. EVPN can provide MAC address learning through control-plane signaling rather than relying exclusively on traditional data-plane flooding. DHCP supplies host configuration, GRE creates generic tunnels, and NDP performs IPv6 neighbor discovery. Therefore, EVPN is the appropriate answer because it is specifically designed to provide Ethernet VPN services across routed infrastructure.

Question 123

Which protocol distributes multicast traffic using shortest-path trees?

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

Correct Answer: 2

Explanation:

Protocol Independent Multicast supports multicast forwarding and can establish shortest-path trees for multicast traffic. In PIM-SM environments, multicast forwarding can initially involve a shared tree and later transition toward source-specific shortest-path forwarding when appropriate. The protocol relies on underlying unicast routing information to determine how multicast packets should travel through the network. VRRP provides default-gateway redundancy, LACP manages link aggregation, and RSTP prevents Layer 2 loops. Therefore, PIM is the correct answer because it provides multicast routing mechanisms that can construct source-based shortest-path forwarding trees.

Question 124

Which Junos feature stores configurations before activation?

1. Rescue configuration
2. Candidate configuration
3. Factory configuration
4. Archived configuration

Correct Answer: 2

Explanation:

The Junos candidate configuration contains configuration changes before they are committed and activated. Administrators can enter configuration mode, make multiple changes, review them, and then use the commit process to validate and activate the resulting configuration. This separation between candidate and active configuration is an important characteristic of Junos configuration management. A rescue configuration provides a known recovery configuration, while archived or factory configurations serve different purposes. Therefore, the candidate configuration is the correct answer because it represents the editable configuration state that exists before successful activation.

Question 125

Which mechanism provides rapid Layer 2 topology reconvergence?

1. MSTP
2. RSTP
3. VPLS
4. MACsec

Correct Answer: 2

Explanation:

Rapid Spanning Tree Protocol, or RSTP, improves Layer 2 convergence compared with traditional Spanning Tree Protocol. It introduces faster mechanisms for recognizing topology changes and transitioning appropriate interfaces between forwarding and non-forwarding states. This allows a switched network to recover from certain topology changes more quickly while still preventing Layer 2 loops. MSTP provides multiple spanning-tree instances, VPLS provides virtual Layer 2 services, and MACsec provides Ethernet-link security. Therefore, RSTP is the correct answer because its primary improvement is faster Layer 2 topology convergence.

Question 126

Which VPN technology connects remote users securely over IP?

1. MPLS
2. GRE
3. IPsec
4. VXLAN

Correct Answer: 3

Explanation:

IPsec provides security services for IP communications and can be used to create encrypted VPN connections across untrusted networks. It supports authentication, integrity protection, and encryption depending on the configured algorithms and architecture. Remote-access and site-to-site VPN designs commonly use IPsec to protect traffic traveling across public or otherwise untrusted infrastructure. MPLS provides label-based forwarding and VPN services without inherently providing encryption, GRE provides tunneling without encryption by itself, and VXLAN provides Layer 2 overlay encapsulation. Therefore, IPsec is the correct answer for securely transporting IP traffic through encrypted VPN connections.

Question 127

Which technology extends Layer 2 segments across routed infrastructure?

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

Correct Answer: 1

Explanation:

Virtual Extensible LAN, or VXLAN, provides Layer 2 network overlays across Layer 3 infrastructure. VXLAN encapsulates Ethernet frames inside IP-based transport packets, allowing logical Layer 2 segments to extend between network locations without requiring the underlying infrastructure to operate as one large Layer 2 domain. This architecture is widely associated with modern data-center fabrics and scalable network virtualization. SNMP provides management information, NTP synchronizes clocks, and Syslog transports event messages. Therefore, VXLAN is the correct answer because it enables Layer 2 connectivity through a Layer 3 transport network.

Question 128

Which protocol synchronizes clocks using hierarchical time sources?

1. LDAP
2. NTP
3. TACACS+
4. RADIUS

Correct Answer: 2

Explanation:

Network Time Protocol, or NTP, synchronizes clocks across networked systems using a hierarchical time-source architecture. Devices can obtain time from configured NTP servers and maintain their local clocks within an acceptable level of synchronization. Accurate time is important for event correlation, logging, authentication systems, troubleshooting, and many other network operations. LDAP is associated with directory services, while TACACS+ and RADIUS are authentication and authorization protocols. Therefore, NTP is the correct answer because it specifically provides network-based clock synchronization through organized time sources.

Question 129

Which Junos service records system events for troubleshooting?

1. SNMP traps
2. Syslog
3. NetFlow
4. DHCP relay

Correct Answer: 2

Explanation:

Syslog provides a standardized mechanism for recording and forwarding system messages and operational events. Junos devices can generate messages for various conditions, including configuration activities, protocol events, authentication events, interface changes, and system conditions. Administrators can configure local or remote logging destinations to retain and analyze these messages. SNMP traps provide event notifications to management systems, NetFlow-style mechanisms provide traffic-flow information, and DHCP relay forwards client requests between network segments. Therefore, Syslog is the correct answer because it is specifically designed to collect and record system and operational event messages.

Question 130

Which tunneling technology encapsulates Layer 2 frames over UDP?

1. VXLAN
2. IPsec
3. GRE
4. PPP

Correct Answer: 1

Explanation:

VXLAN encapsulates Ethernet frames within UDP packets, allowing Layer 2 networks to be transported across Layer 3 infrastructure. Its use of UDP enables scalable overlay networking and allows the underlay network to provide ordinary IP forwarding between tunnel endpoints. VXLAN also introduces a large virtual network identifier space compared with traditional VLAN numbering, making it suitable for large-scale virtualization environments. IPsec provides secure IP communication, GRE provides generic encapsulation, and PPP is a point-to-point data-link protocol. Therefore, VXLAN is the correct answer because it specifically carries Layer 2 Ethernet traffic using UDP-based encapsulation.

Question 131

Which protocol provides authentication and authorization for administrators?

1. TFTP
2. TACACS+
3. LLDP
4. RSVP

Correct Answer: 2

Explanation:

TACACS+ is an AAA protocol commonly used to provide centralized authentication, authorization, and accounting for network-device administrators. It separates authentication and authorization functions and can provide detailed control over what authenticated administrators are permitted to do. Centralized AAA also helps organizations manage administrative access consistently across multiple network devices. TFTP is a lightweight file-transfer protocol, LLDP provides neighbor discovery, and RSVP supports resource reservation signaling. Therefore, TACACS+ is the correct answer because it is specifically designed for centralized administrative access control and AAA services.

Question 132

Which mechanism exports traffic-flow statistics for network analysis?

1. NetFlow
2. ARP
3. BFD
4. STP

Correct Answer: 1

Explanation:

NetFlow and similar flow-monitoring technologies collect information about traffic flows passing through network devices. Flow records can include details such as source and destination addresses, ports, protocol information, packet counts, byte counts, and timestamps. These records can then be exported to monitoring or analysis systems for capacity planning, troubleshooting, accounting, and traffic-pattern analysis. ARP performs address resolution, BFD detects forwarding failures, and STP prevents Layer 2 loops. Therefore, NetFlow is the correct answer because its purpose is to provide summarized traffic-flow information for centralized analysis.

Question 133

Which routing technique combines multiple prefixes into one?

1. Route reflection
2. Prefix aggregation
3. Metric propagation
4. Neighbor discovery

Correct Answer: 2

Explanation:

Prefix aggregation combines multiple more-specific network prefixes into a broader summary prefix when the network design permits such summarization. This can reduce the number of routes carried through routing tables and can make routing information more manageable. Aggregation can also help limit unnecessary propagation of individual prefixes between routing domains. Route reflection addresses BGP scalability by reducing the need for full-mesh iBGP, metric propagation concerns routing attributes, and neighbor discovery identifies directly connected devices. Therefore, prefix aggregation is the correct answer because it summarizes multiple routes into a broader representation.

Question 134

Which protocol supports secure Layer 2 frame authentication?

1. MACsec
2. VXLAN
3. MPLS
4. LDP

Correct Answer: 1

Explanation:

MACsec, defined by IEEE 802.1AE, provides security for Ethernet frames at the data-link layer. It can offer confidentiality, integrity, data-origin authentication, and protection against certain replay attacks depending on the implementation and configuration. MACsec is useful when Ethernet traffic needs protection directly across a Layer 2 link. VXLAN provides overlay encapsulation, MPLS provides label-based forwarding, and LDP distributes labels for MPLS forwarding. Therefore, MACsec is the correct answer because it specifically provides security mechanisms for Ethernet frames at Layer 2.

Question 135

Which BGP mechanism reduces internal peer-session requirements?

1. Confederation
2. Route reflection
3. MED adjustment
4. Prefix suppression

Correct Answer: 2

Explanation:

BGP route reflection reduces the need for every internal BGP router to maintain a direct session with every other internal BGP router. A route reflector can receive routes from clients and reflect eligible routes to other clients or peers according to BGP rules. This helps improve scalability in large autonomous systems by reducing the number of required iBGP sessions. Confederations provide another BGP scalability technique by dividing an autonomous system into smaller internal sub-autonomous systems, but route reflection directly addresses the full-mesh session requirement through centralized reflection behavior. Therefore, route reflection is the correct answer.

Question 136

Which protocol detects duplicate IPv6 address usage?

1. DAD
2. FTP
3. LACP
4. RSVP

Correct Answer: 1

Explanation:

Duplicate Address Detection, or DAD, is part of IPv6 Neighbor Discovery and helps determine whether an IPv6 address is already being used on the local link before an interface begins using it. The node performs the procedure using Neighbor Solicitation messaging and examines whether another device responds for the same address. Detecting duplicate addressing helps prevent communication problems caused by multiple interfaces attempting to use the same IPv6 address. FTP handles file transfers, LACP manages link aggregation, and RSVP supports signaling functions. Therefore, DAD is the correct answer because it specifically detects duplicate IPv6 addresses.

Question 137

Which Junos command compares candidate and active configurations?

1. show | compare
2. show configuration
3. display set
4. request system snapshot

Correct Answer: 1

Explanation:

The Junos show | compare command is used in configuration mode to display differences between the candidate configuration and the currently active configuration. This makes it useful for reviewing pending changes before committing them. Administrators can inspect exactly which statements have been added, removed, or modified and can identify unintended changes before activation. show configuration displays configuration information, display set is associated with viewing configuration statements in set-style syntax, and the snapshot command concerns system recovery data. Therefore, show | compare is the correct answer for reviewing candidate-versus-active configuration differences.

Question 138

Which mechanism prevents unauthorized MAC addresses from accessing ports?

1. Port security
2. Route leaking
3. Prefix delegation
4. Path selection

Correct Answer: 1

Explanation:

Port security provides mechanisms for controlling which MAC addresses are permitted to use a switch interface. Depending on platform capabilities, administrators can restrict the number or identity of MAC addresses learned or accepted on a port. This can help limit unauthorized endpoint access and reduce certain Layer 2 security risks. Route leaking concerns sharing routes between routing instances, prefix delegation distributes address prefixes, and path selection determines routing choices. Therefore, port security is the correct answer because it directly addresses access control based on Layer 2 endpoint identities associated with switch ports.

Question 139

Which IPv6 mechanism automatically configures host addresses?

1. SLAAC
2. FTP
3. NAT
4. GRE

Correct Answer: 1

Explanation:

Stateless Address Autoconfiguration, or SLAAC, allows IPv6 hosts to automatically configure addresses using information advertised by routers. Router Advertisement messages can provide network-prefix information that enables a host to construct an IPv6 address without requiring a traditional DHCPv6 address-assignment process. SLAAC can simplify deployment because hosts can configure themselves based on information received from the local IPv6 network. FTP provides file transfer, NAT translates addresses in applicable environments, and GRE provides tunneling. Therefore, SLAAC is the correct answer because it provides automatic IPv6 address configuration through router advertisements.

Question 140

Which protocol carries authentication packets between network devices?

1. RADIUS
2. OSPF
3. PIM
4. LACP

Correct Answer: 1

Explanation:

RADIUS is an AAA protocol that carries authentication, authorization, and accounting information between network access devices and a centralized authentication server. It is commonly used when network devices need to verify user credentials against a central service rather than maintaining independent authentication databases. RADIUS can support network-access authentication and related policy decisions depending on the deployment. OSPF exchanges routing information, PIM manages multicast forwarding, and LACP negotiates link aggregation. Therefore, RADIUS is the correct answer because it is specifically designed to transport AAA-related information between network infrastructure and authentication services.