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Question 21

Which protocol provides fast neighbor failure detection?

1. RSVP
2. BFD
3. LDP
4. SNMP

Correct Answer: 2

Explanation:

Bidirectional Forwarding Detection, or BFD, is designed to detect failures between neighboring network devices very quickly. It establishes a lightweight session between endpoints and continuously exchanges control packets. If expected packets stop arriving within the configured detection interval, BFD declares the session down. Routing protocols can then use this information to react without waiting for their own longer hold or dead timers to expire. RSVP performs signaling functions, LDP distributes MPLS labels, and SNMP supports network management. Therefore, BFD is the correct choice because its primary purpose is rapid detection of forwarding-path or neighboring-device failures.

Question 22

Which OSPF component contains topology information?

1. Routing policy
2. Forwarding table
3. Link-state database
4. Interface queue

Correct Answer: 3

Explanation:

The OSPF link-state database contains information describing the topology of an OSPF routing domain. Routers exchange link-state advertisements, allowing participating devices to construct a synchronized view of network connectivity. Each router then uses its local database as input to the Shortest Path First algorithm when calculating routes. The resulting routes are installed into the routing table when appropriate. A routing policy controls route handling, a forwarding table supports packet forwarding, and an interface queue stores packets awaiting transmission. Therefore, the link-state database is the OSPF component that maintains the topology information required for path calculation.

Question 23

What transport protocol does BGP use for sessions?

1. UDP
2. ICMP
3. TCP
4. GRE

Correct Answer: 3

Explanation:

BGP uses TCP as its transport protocol, specifically establishing sessions through TCP port 179. TCP provides reliable, ordered delivery of BGP messages between neighboring speakers. This allows BGP to focus on exchanging routing information without needing to implement its own reliable transport mechanism. UDP does not provide the same connection-oriented reliability, while ICMP is primarily used for control and diagnostic messaging. GRE is a tunneling protocol rather than BGP’s transport mechanism. Therefore, TCP is the correct answer. Understanding BGP’s reliance on TCP is important when troubleshooting peer connectivity, firewall policies, and session-establishment problems.

Question 24

Which protocol supports multicast routing decisions?

1. PIM
2. LDP
3. BFD
4. NTP

Correct Answer: 1

Explanation:

Protocol Independent Multicast, or PIM, is used to build multicast distribution trees and make forwarding decisions for multicast traffic. PIM operates independently of a particular unicast routing protocol, instead using available unicast routing information to determine reachable paths. Different PIM modes can support different multicast deployment requirements. LDP distributes MPLS label bindings, BFD detects forwarding failures, and NTP synchronizes device clocks. None of these protocols performs the multicast routing function described in the question. Therefore, PIM is the correct answer because it provides the mechanisms required to establish and maintain multicast forwarding paths.

Question 25

Which BGP attribute indicates the next-hop router?

1. MED
2. Origin
3. Next Hop
4. Community

Correct Answer: 3

Explanation:

The BGP Next Hop attribute identifies the IP address that should be used as the next-hop destination when forwarding traffic toward an advertised prefix. BGP speakers include next-hop information with route advertisements, although the exact behavior can vary depending on whether routes are exchanged through external or internal BGP sessions. MED is used to influence entry-point selection by another autonomous system. Origin indicates how a route was introduced into BGP, while Community provides a mechanism for grouping routes and applying policies. Therefore, Next Hop is the correct attribute because it identifies the address associated with forwarding toward the advertised network.

Question 26

Which MPLS device forwards packets using labels?

1. Label Switching Router
2. DNS resolver
3. DHCP server
4. Syslog collector

Correct Answer: 1

Explanation:

A Label Switching Router, or LSR, is an MPLS-capable router that forwards packets based on MPLS labels. Depending on its position within the label-switched path, an LSR can perform operations such as label swapping, pushing, or popping. MPLS forwarding allows packets belonging to particular forwarding equivalence classes to receive consistent treatment through the network. A DNS resolver handles name resolution, a DHCP server provides network configuration, and a Syslog collector receives event messages. These systems do not perform MPLS label forwarding. Therefore, the Label Switching Router is the correct answer for the device described in the question.

Question 27

Which BGP attribute generally prefers higher values?

1. Local Preference
2. MED
3. Origin
4. Weightless Metric

Correct Answer: 1

Explanation:

BGP generally prefers a higher Local Preference value when comparing otherwise suitable routes. Local Preference is used within an autonomous system to influence outbound traffic, allowing administrators to select preferred exit points for external destinations. Because the attribute is propagated through the internal BGP environment, multiple routers can apply a consistent outbound-routing policy. MED behaves differently because lower values are generally preferred during applicable comparisons. Origin is evaluated as part of BGP route selection but does not represent a simple higher-is-better metric. Therefore, Local Preference is the correct answer because BGP normally favors the route carrying the higher value.

Question 28

Which routing protocol uses hop count as its metric?

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

Correct Answer: 3

Explanation:

RIP, or Routing Information Protocol, uses hop count as its primary routing metric. Each router hop toward a destination increases the metric by one, and routes exceeding the protocol’s maximum hop-count limit are considered unreachable. This simple approach makes RIP easy to understand but limits its usefulness in large or complex networks. OSPF calculates paths using interface costs, while IS-IS uses configurable link metrics. BGP relies on a collection of path attributes and policy-based selection rather than hop count as its primary metric. Therefore, RIP is the correct answer because hop count is its defining routing metric.

Question 29

Which Junos mode displays operational device information?

1. Configuration mode
2. Operational mode
3. Private mode
4. Template mode

Correct Answer: 2

Explanation:

Operational mode in Junos is used to monitor the device, inspect operational status, troubleshoot problems, and execute commands that display current network conditions. Common operational commands include show interfaces, show route, and show system uptime. Configuration mode serves a different purpose: administrators use it to create, modify, and manage the device’s candidate configuration. Private mode is related to how configuration work can be isolated among users, while template mode is not the standard Junos operating mode described here. Therefore, operational mode is the correct answer for viewing and managing live device information.

Question 30

Which protocol provides device discovery at Layer 2?

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

Correct Answer: 1

Explanation:

LLDP, or Link Layer Discovery Protocol, enables directly connected network devices to exchange identification and capability information at Layer 2. A switch or router can advertise information such as its system identity, interface details, and supported capabilities to neighboring devices. This information can assist network administrators with topology verification and troubleshooting. BGP exchanges routing information between peers, OSPF provides interior routing, and RSVP supports signaling functions. None of these protocols is intended primarily for Layer 2 neighbor discovery. Therefore, LLDP is the correct answer because it specifically provides standardized discovery information between directly connected network devices.

Question 31

Which MPLS term identifies packets receiving identical forwarding treatment?

1. FEC
2. VRF
3. ASN
4. VLAN

Correct Answer: 1

Explanation:

A Forwarding Equivalence Class, or FEC, identifies packets that should receive the same forwarding treatment within an MPLS environment. Packets assigned to the same FEC can follow the same label-switched path or receive equivalent forwarding behavior. MPLS labels are associated with FECs to help routers determine how packets should be handled. VRF provides separate routing and forwarding contexts, ASN identifies an autonomous system, and VLAN provides Layer 2 segmentation. These concepts are important in networking but have different purposes. Therefore, FEC is the correct answer because it specifically represents a group of packets receiving equivalent forwarding treatment.

Question 32

Which protocol synchronizes network device clocks?

1. LLDP
2. NTP
3. BFD
4. LDP

Correct Answer: 2

Explanation:

Network Time Protocol, or NTP, synchronizes clocks between network devices and time sources. Consistent time is valuable for troubleshooting, event correlation, authentication systems, logging, and operational monitoring. NTP allows devices to maintain clocks that closely correspond to a reliable reference source. LLDP provides neighbor discovery information, BFD detects forwarding failures, and LDP distributes MPLS labels. These protocols do not perform network-wide clock synchronization. Therefore, NTP is the correct answer because its primary purpose is maintaining consistent time across participating network devices, which helps administrators accurately interpret events and correlate logs generated by different systems.

Question 33

Which BGP message maintains an established session?

1. OPEN
2. UPDATE
3. KEEPALIVE
4. NOTIFICATION

Correct Answer: 3

Explanation:

BGP KEEPALIVE messages help maintain an established BGP session by allowing peers to confirm that the relationship remains active. These messages are exchanged periodically when there is no other BGP traffic sufficient to demonstrate continued communication. If a peer stops receiving expected messages within the negotiated hold time, it can consider the session unavailable. OPEN messages establish initial session parameters, UPDATE messages advertise or withdraw routing information, and NOTIFICATION messages communicate errors. Therefore, KEEPALIVE is the correct answer because it supports continued operation of an established BGP peering relationship.

Question 34

Which technology separates customer routing information?

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

Correct Answer: 1

Explanation:

Virtual Routing and Forwarding, or VRF, separates routing information by maintaining independent routing tables and forwarding contexts. Service providers commonly use VRFs to isolate different customer networks while sharing the same physical infrastructure. This separation also allows customers to use overlapping IP address spaces without creating conflicts between their routing information. LACP combines physical links into a logical aggregated connection, STP prevents Layer 2 switching loops, and LLDP provides neighbor discovery. Therefore, VRF is the correct technology because it directly addresses the requirement for independent customer-specific routing environments within a shared network infrastructure.

Question 35

Which protocol is an Interior Gateway Protocol?

1. BGP
2. OSPF
3. LDP
4. SNMP

Correct Answer: 2

Explanation:

OSPF is an Interior Gateway Protocol used to exchange routing information within an autonomous system. It is a link-state protocol that maintains topology information and calculates paths using the Shortest Path First algorithm. OSPF can support hierarchical designs through areas, making it suitable for larger internal networks. BGP is primarily an exterior gateway protocol, while LDP distributes MPLS labels rather than serving as a general-purpose IGP. SNMP is a network management protocol used for monitoring and management. Therefore, OSPF is the correct answer because it specifically provides interior routing functionality within an autonomous system.

Question 36

Which BGP attribute helps influence inbound traffic?

1. Local Preference
2. MED
3. Weight
4. Cluster ID

Correct Answer: 2

Explanation:

MED, or Multi-Exit Discriminator, can be used to influence how a neighboring autonomous system selects an entry point into the advertising network. When multiple connections exist between autonomous systems, an administrator can advertise different MED values to indicate a preferred ingress path. Lower MED values are generally preferred when the relevant BGP comparison is performed. Local Preference primarily influences outbound traffic within the local autonomous system. Weight is a local implementation-specific preference, while Cluster ID is associated with route-reflector operation. Therefore, MED is the appropriate answer for influencing inbound path selection from a neighboring autonomous system.

Question 37

Which protocol is primarily used for network management monitoring?

1. SNMP
2. OSPF
3. RSVP
4. PIM

Correct Answer: 1

Explanation:

Simple Network Management Protocol, or SNMP, is widely used to monitor and manage network devices. Management systems can use SNMP to retrieve operational information such as interface statistics, device status, and other supported management data. SNMP can also support notifications that inform management platforms about selected events. OSPF handles internal routing, RSVP provides signaling functions, and PIM manages multicast routing behavior. These protocols therefore serve different purposes from network management. SNMP is the correct answer because its primary role is exchanging management information between network devices and management systems for monitoring and operational administration.

Question 38

Which routing table contains active routes in Junos?

1. inet.0
2. mpls.0
3. inet6.3
4. iso.0

Correct Answer: 1

Explanation:

The inet.0 routing table is the primary IPv4 unicast routing table in Junos. It contains active IPv4 routes used for normal IP forwarding unless a different routing instance or table is involved. The mpls.0 table is associated with MPLS-related forwarding information, while inet6.3 is associated with IPv6 routing information in specific contexts. iso.0 is associated with ISO addressing information. Understanding Junos routing-table names is important when troubleshooting route installation and forwarding behavior. Therefore, inet.0 is the correct answer for the standard IPv4 unicast routing table.

Question 39

Which protocol uses TCP port 179 by default?

1. LDP
2. OSPF
3. BGP
4. BFD

Correct Answer: 3

Explanation:

BGP uses TCP port 179 for establishing communication between neighboring BGP speakers. Using TCP provides reliable, ordered delivery of routing messages and allows BGP to maintain a connection-oriented session with its peer. This port information is useful during troubleshooting because firewalls, filters, and security policies must permit appropriate BGP traffic for a session to form. LDP uses its own transport mechanisms, OSPF operates directly over IP rather than TCP, and BFD can operate through different encapsulation methods depending on its application. Therefore, BGP is the protocol associated with TCP port 179.

Question 40

Which Junos command displays interface operational status?

1. show route
2. show interfaces
3. show system users
4. show chassis alarms

Correct Answer: 2

Explanation:

The Junos show interfaces command displays operational information about network interfaces. Its output can include whether an interface is administratively enabled, whether the physical link is operational, interface addresses, packet counters, and other useful status information. Administrators commonly use this command when investigating connectivity or interface-related problems. show route examines routing information, show system users displays logged-in users, and show chassis alarms focuses on system alarms. Therefore, show interfaces is the correct command for checking interface operational status and obtaining basic information about the condition of network interfaces.