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Question 281

Which Junos service automatically records operational system messages?

1. Syslog
2. NETCONF
3. RADIUS
4. DHCP

Correct Answer: 1

Explanation:

Syslog provides a mechanism for recording and forwarding system-generated messages. Junos devices can generate messages related to system operations, interfaces, authentication, routing, hardware conditions, and other events. Administrators can configure local or remote logging destinations according to operational requirements. Centralized logging is especially useful when troubleshooting because events from multiple network devices can be correlated using timestamps. NETCONF is primarily used for structured management, RADIUS provides centralized authentication services, and DHCP provides host configuration. Syslog therefore serves the specific purpose of collecting and managing operational messages generated by network devices.

Question 282

Which Junos command displays learned IPv4 neighbor mappings?

1. show arp
2. show route terse
3. show ethernet-switching table
4. show ipv6 neighbors

Correct Answer: 1

Explanation:

The show arp command displays Address Resolution Protocol information for IPv4 neighbors. ARP maintains mappings between IPv4 addresses and corresponding Layer 2 hardware addresses on directly connected networks. When troubleshooting IPv4 connectivity, administrators can inspect this information to determine whether the device successfully resolved the expected neighbor address. An incomplete or unexpected mapping may indicate an issue with local connectivity, address resolution, or endpoint availability. The Ethernet switching table contains learned MAC addresses, while IPv6 uses Neighbor Discovery instead of ARP. Therefore, show arp is the appropriate Junos command for examining IPv4 ARP mappings.

Question 283

Which protocol carries authentication requests to centralized servers?

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

Correct Answer: 1

Explanation:

RADIUS is a protocol commonly used to provide centralized authentication, authorization, and accounting services for network access and administrative environments. A network device can forward authentication requests to a RADIUS server instead of maintaining every credential locally. This allows organizations to manage authentication centrally and apply consistent access policies. NTP synchronizes clocks, SNMP provides network-management information, and LLDP discovers neighboring devices. RADIUS therefore serves a different operational purpose by handling authentication-related exchanges with a centralized server. Proper configuration requires the network device and RADIUS server to share compatible authentication parameters and credentials.

Question 284

Which Junos mechanism applies traffic treatment based on forwarding classes?

1. CoS
2. ARP
3. BGP
4. LLDP

Correct Answer: 1

Explanation:

Class of Service, or CoS, provides mechanisms for classifying and treating traffic according to defined service requirements. Forwarding classes can identify different categories of traffic, which can then receive specific queueing, scheduling, marking, or other treatment. This allows administrators to prioritize important applications and manage traffic during periods of congestion. ARP handles IPv4 address resolution, BGP exchanges routing information, and LLDP discovers neighboring devices. CoS therefore focuses on traffic handling and quality-of-service behavior rather than basic addressing, routing, or topology discovery. Proper CoS design depends on consistent classification and queueing policies throughout the network.

Question 285

Which Junos command reveals detailed routing protocol neighbor information?

1. show bgp neighbor
2. show system users
3. show chassis alarms
4. show interfaces media

Correct Answer: 1

Explanation:

The show bgp neighbor command provides detailed operational information about BGP peer relationships. Depending on the platform and configuration, the output can include peer addresses, session states, negotiated capabilities, message statistics, timers, and route advertisement information. This makes the command particularly useful when troubleshooting BGP sessions that are not establishing correctly or are behaving unexpectedly. System-user information, chassis alarms, and interface media details address different operational areas. Examining BGP neighbor information can help administrators determine whether a peer is established, what capabilities were negotiated, and whether messages are being exchanged normally.

Question 286

Which Junos mechanism limits broadcast, multicast, or unknown-unicast traffic?

1. Storm control
2. Route reflection
3. Prefix aggregation
4. Address resolution

Correct Answer: 1

Explanation:

Storm control limits excessive Layer 2 traffic such as broadcast, multicast, or unknown-unicast traffic on supported interfaces. Without appropriate controls, a traffic storm can consume significant bandwidth and affect other devices within the broadcast domain. Storm-control mechanisms allow administrators to establish thresholds and define how excessive traffic should be handled. Route reflection concerns BGP scalability, prefix aggregation reduces routing information, and address resolution maps network-layer addresses to Layer 2 identifiers. Storm control therefore addresses excessive Layer 2 traffic conditions rather than routing-table management or neighbor discovery.

Question 287

Which IPv6 protocol communicates router discovery information to hosts?

1. ICMPv6
2. TCP
3. UDP
4. ARP

Correct Answer: 1

Explanation:

IPv6 router discovery is performed using ICMPv6 Neighbor Discovery messages. Router Solicitation and Router Advertisement messages allow hosts and routers to exchange information about local network configuration and available routers. Router Advertisements can provide information such as prefixes, default-router availability, and address-autoconfiguration behavior. TCP and UDP provide transport-layer communication, while ARP is associated with IPv4 address resolution. ICMPv6 therefore provides the protocol framework used for IPv6 router discovery. Understanding this relationship is important when troubleshooting IPv6 hosts that are unable to learn default-router or prefix information automatically.

Question 288

Which BGP attribute can influence inbound traffic toward an autonomous system?

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

Correct Answer: 1

Explanation:

The BGP Multi-Exit Discriminator, or MED, can influence how neighboring autonomous systems choose among multiple entry points into a network. When an autonomous system advertises multiple paths to another autonomous system, MED can provide a preference indication for incoming traffic under applicable BGP selection conditions. Local Preference serves primarily as an internal attribute for choosing outbound paths within an autonomous system. Originator ID and Cluster ID support route-reflection behavior. MED should not be treated as an absolute guarantee of inbound traffic flow because remote policy and other path-selection factors can override it.

Question 289

Which Junos command displays chassis hardware inventory information?

1. show chassis hardware
2. show system storage
3. show system core-dumps
4. show interfaces descriptions

Correct Answer: 1

Explanation:

The show chassis hardware command displays hardware inventory information for the Junos device. Depending on the platform, the output can identify components such as chassis modules, Routing Engines, FPCs, PICs, power supplies, and other installed hardware. This information is useful when verifying hardware installation, identifying component versions, or preparing for maintenance. Storage information focuses on filesystem resources, core-dump commands concern diagnostic crash files, and interface descriptions provide logical interface documentation. Hardware inventory is therefore best examined using the chassis hardware command.

Question 290

Which routing mechanism prevents loops by checking autonomous system history?

1. AS Path
2. MED
3. Community
4. Local Preference

Correct Answer: 1

Explanation:

BGP uses the AS Path attribute as an important loop-prevention mechanism. When a route is advertised between autonomous systems, the originating or propagating AS information is added to the path. If a BGP router receives a route containing its own autonomous system number, it can reject the route because the route has effectively returned to its originating AS. This prevents many interdomain routing loops. MED influences certain path-selection decisions, Community carries policy tags, and Local Preference influences internal outbound-path selection. AS Path therefore has a fundamental role in both BGP path selection and loop prevention.

Question 291

Which Junos routing instance type supports separate customer VPN tables?

1. VRF
2. Virtual-router
3. Forwarding
4. No-forwarding

Correct Answer: 1

Explanation:

A Virtual Routing and Forwarding, or VRF, routing instance is designed to maintain a separate routing table for a particular VPN or customer environment. VRFs allow multiple customers or logical networks to use overlapping address spaces while maintaining routing separation. In Layer 3 VPN architectures, provider-edge devices use VRF instances to keep customer routes distinct. Other routing-instance types have different purposes. Virtual-router instances provide routing separation without necessarily implementing the complete VPN behavior of a VRF, while forwarding and no-forwarding instances are used for other specialized designs. VRF is therefore strongly associated with customer VPN routing tables.

Question 292

Which protocol enables IPv6 multicast listener management?

1. MLD
2. IGMP
3. PIM
4. MSDP

Correct Answer: 1

Explanation:

Multicast Listener Discovery, or MLD, manages IPv6 multicast group membership on local network segments. IPv6 hosts can use MLD messages to indicate interest in receiving traffic for specific multicast groups, while routers use that information to determine whether multicast traffic should be forwarded toward local listeners. IGMP performs a similar role for IPv4 multicast, while PIM establishes multicast forwarding between routers. MSDP can exchange multicast source information between routing domains. MLD is therefore the appropriate protocol when discussing IPv6 multicast listener membership rather than multicast routing or IPv4 multicast membership.

Question 293

Which Junos feature allows traffic inspection through a copied interface stream?

1. Port mirroring
2. Route leaking
3. ECMP
4. Prefix filtering

Correct Answer: 1

Explanation:

Port mirroring creates a copy of selected traffic and sends that copy toward a designated monitoring interface. A connected packet analyzer can inspect the mirrored traffic without directly participating in normal forwarding. This capability is useful for troubleshooting, security analysis, protocol inspection, and performance investigations. Route leaking controls the exchange of routes between routing instances, ECMP distributes traffic over equivalent paths, and prefix filtering controls which routes match policy conditions. Port mirroring therefore focuses on obtaining visibility into network traffic while leaving the original forwarding behavior intact.

Question 294

Which BGP feature carries IPv6 unicast routes between peers?

1. MP-BGP
2. Route Damping
3. TCP MD5
4. Graceful Restart

Correct Answer: 1

Explanation:

Multiprotocol BGP, or MP-BGP, allows BGP to carry reachability information for address families beyond traditional IPv4 unicast. IPv6 unicast routing can be exchanged between BGP peers when the relevant address-family capability is enabled. This makes MP-BGP important in networks where IPv6 connectivity is exchanged through BGP. Route Damping handles unstable routes, TCP authentication protects BGP session communication, and Graceful Restart supports continuity during certain control-plane restart conditions. MP-BGP therefore provides the capability required for BGP peers to exchange IPv6 unicast reachability information.

Question 295

Which Junos command displays routing table entries in compact format?

1. show route terse
2. show route detail
3. show route summary
4. show route extensive

Correct Answer: 1

Explanation:

The show route terse command provides a compact representation of routing-table information. It is useful when administrators need to quickly review available routes without the extensive detail produced by more verbose commands. The output can help identify route destinations, protocol sources, and basic route-selection information. show route detail provides more information about individual routes, while summary output focuses on overall routing-table statistics. A terse view is therefore convenient during initial troubleshooting or when a quick routing-table overview is needed before examining individual routes in greater depth.

Question 296

Which Ethernet protocol negotiates bundled physical links automatically?

1. LACP
2. STP
3. LLDP
4. 802.1X

Correct Answer: 1

Explanation:

Link Aggregation Control Protocol, or LACP, dynamically negotiates the formation and maintenance of link aggregation groups between compatible devices. Multiple physical Ethernet links can be combined into a logical aggregated interface, providing increased capacity and redundancy. LACP exchanges control information between participating devices to determine whether links can operate as part of the aggregation. STP prevents Layer 2 loops, LLDP discovers neighboring devices, and 802.1X controls network access through authentication. LACP is therefore specifically associated with negotiating and maintaining aggregated Ethernet links.

Question 297

Which Junos command compares pending configuration against active settings?

1. show | compare
2. show configuration
3. show system commit
4. show system rollback

Correct Answer: 1

Explanation:

The show | compare command displays differences between the candidate configuration and the currently active configuration. This allows administrators to review pending changes before committing them. The comparison can reveal added, modified, or deleted statements, helping prevent accidental activation of unwanted changes. show configuration displays configuration information but does not specifically provide the same candidate-versus-active comparison. Commit history and rollback commands provide information about previous configuration states. Reviewing the comparison before committing is a useful operational practice when managing complex Junos configurations.

Question 298

Which mechanism distributes packets across multiple aggregated links?

1. Link aggregation hashing
2. Router advertisements
3. Route reflection
4. Prefix delegation

Correct Answer: 1

Explanation:

Link aggregation commonly uses a hashing mechanism to determine which physical member link should carry a particular traffic flow. Hash inputs can include supported packet attributes such as source and destination addresses or ports. The goal is to distribute different flows across the available member links while typically keeping packets belonging to the same flow on a consistent physical path. Router Advertisements provide IPv6 configuration information, route reflection distributes BGP routes, and prefix delegation allocates IPv6 prefixes. Link aggregation hashing therefore concerns traffic distribution within an aggregated Ethernet connection.

Question 299

Which Junos feature provides traffic statistics through packet sampling?

1. J-Flow
2. NTP
3. LLDP
4. DHCP

Correct Answer: 1

Explanation:

J-Flow is Juniper’s flow-monitoring technology for collecting traffic-flow information through packet sampling and related statistics. It can provide visibility into traffic patterns, source and destination information, protocols, and other flow characteristics depending on the configuration and platform. Network administrators can use flow information for traffic analysis, capacity planning, troubleshooting, and security investigations. NTP synchronizes clocks, LLDP discovers neighboring devices, and DHCP provides host configuration. J-Flow therefore focuses on understanding traffic behavior rather than network time, topology discovery, or address assignment.

Question 300

Which Junos feature can automatically discard excessive traffic rates?

1. Policer
2. Scheduler
3. Classifier
4. Rewrite rule

Correct Answer: 1

Explanation:

A policer controls traffic according to configured rate and burst parameters. When traffic exceeds the permitted rate, the policer can apply the configured action to the excess traffic, which may include discarding packets. This makes policing useful for enforcing bandwidth limits and preventing excessive traffic from consuming network resources. A scheduler controls how queued traffic receives transmission opportunities, a classifier determines traffic classification, and a rewrite rule changes packet markings. Policing therefore focuses on rate enforcement rather than queue scheduling or packet classification. The exact behavior depends on the configured policer parameters and platform capabilities.