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Question 241

Which Junos command displays active firewall filter counters?

1. show firewall
2. show policy
3. show security flow
4. show firewall family inet

Correct Answer: 1

Explanation:

The show firewall command provides operational information about configured firewall filters and their associated counters. Firewall filters can contain terms that classify packets according to conditions such as addresses, protocols, ports, or other packet characteristics. Counters help administrators determine whether traffic is matching particular filter terms. This is valuable when troubleshooting filtering behavior because the configuration alone does not always reveal whether packets are actually reaching a specific term. Monitoring counters can also help verify that a newly configured filter is processing the expected traffic. The exact displayed information can vary according to platform and filter family.

Question 242

Which BGP attribute influences route selection inside one autonomous system?

1. MED
2. Local Preference
3. Origin
4. Aggregator

Correct Answer: 2

Explanation:

Local Preference is a BGP attribute used within an autonomous system to influence which exit path is preferred for outbound traffic. A higher Local Preference value is generally preferred during BGP path selection. Because the attribute is propagated within the autonomous system, administrators can use it to establish preferred exit points across multiple internal BGP speakers. MED has a different role and can influence path selection between neighboring autonomous systems under applicable conditions. Origin describes how a route entered BGP, while Aggregator carries information associated with route aggregation. Local Preference is therefore particularly important for controlling internal outbound-path decisions.

Question 243

Which Junos mechanism automatically executes commands based on event conditions?

1. Event policy
2. Static configuration
3. Interface scheduler
4. Route reflector

Correct Answer: 1

Explanation:

Junos event policies provide event-driven automation by allowing administrators to define conditions and corresponding actions. When a configured event occurs, the device can perform specified actions such as executing operational commands or generating notifications. This capability can reduce manual intervention for predictable operational situations. For example, an administrator could create an event policy that reacts to a particular system condition and performs a predefined diagnostic action. Static configuration simply defines device behavior, an interface scheduler is not the general event-policy mechanism, and route reflection concerns BGP route distribution. Event policies are therefore central to Junos event-based automation.

Question 244

Which protocol provides secure command-line access to Junos devices?

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

Correct Answer: 3

Explanation:

Secure Shell, or SSH, provides encrypted remote command-line access to Junos devices. It protects administrative sessions by encrypting information exchanged between the administrator and the device, including authentication credentials and command traffic. SSH is therefore commonly preferred for secure remote management. Telnet does not provide the same level of session encryption, while FTP and TFTP are primarily file-transfer protocols rather than interactive secure management protocols. Administrators should use appropriate authentication and access-control policies alongside SSH to protect management access. SSH is an important component of secure operational management for network infrastructure.

Question 245

Which Junos command displays the device’s current uptime information?

1. show system uptime
2. show system reboot
3. show system snapshot
4. show system core-dumps

Correct Answer: 1

Explanation:

The show system uptime command displays information about how long the Junos device and relevant system components have been running. Uptime information can help administrators determine when a device last restarted and can provide useful context during troubleshooting. For example, an unexpectedly short uptime may indicate a recent reboot, power interruption, or other restart event. The command is different from snapshot and core-dump commands, which address system files and diagnostic information. Reviewing uptime alongside logs, alarms, and commit history can help establish a timeline when investigating unexpected device behavior.

Question 246

Which BGP mechanism suppresses unstable routes temporarily?

1. Graceful Restart
2. Route Damping
3. Add-Path
4. Multipath

Correct Answer: 2

Explanation:

BGP Route Damping is designed to reduce the impact of unstable routes that repeatedly disappear and reappear. A route that flaps frequently can receive a penalty, and when the accumulated penalty reaches a configured threshold, the route can be suppressed temporarily. Over time, the penalty decreases according to configured decay behavior, allowing the route to become eligible again. This mechanism can reduce excessive routing churn caused by unstable prefixes. Graceful Restart addresses control-plane restart behavior, Add-Path supports multiple path advertisements, and Multipath allows multiple eligible paths to be installed. Route Damping specifically targets route instability and repeated flapping.

Question 247

Which Junos command displays installed route statistics and table summaries?

1. show route summary
2. show route receive-protocol
3. show route forwarding-table
4. show route advertising-protocol

Correct Answer: 1

Explanation:

The show route summary command provides a summarized view of routing-table information and route statistics. It can help administrators quickly understand the number and general categories of routes present without displaying every individual route. This makes the command useful for obtaining an overall routing-table snapshot during troubleshooting or operational checks. The forwarding-table command examines forwarding information, while receive-protocol and advertising-protocol commands focus on routes received from or advertised to particular routing peers. A summary view is therefore appropriate when the goal is to understand the overall size and composition of the routing table.

Question 248

Which technology provides encrypted protection for Ethernet frames?

1. MACsec
2. GRE
3. MPLS
4. LACP

Correct Answer: 1

Explanation:

MACsec, defined by IEEE 802.1AE, provides security for Ethernet frames by offering Layer 2 confidentiality and integrity protection. It operates at the Ethernet layer and can protect traffic traveling across supported physical or logical Ethernet connections. MACsec differs from IPsec, which secures traffic at the IP layer, and from GRE, which provides tunneling rather than encryption by itself. MPLS performs label-based forwarding, while LACP negotiates link aggregation. MACsec is therefore specifically designed to protect Ethernet traffic against threats such as unauthorized observation or modification when supported by the participating devices.

Question 249

Which Junos feature allows configuration inheritance across interfaces?

1. Configuration groups
2. Routing instances
3. Firewall policers
4. Forwarding classes

Correct Answer: 1

Explanation:

Junos configuration groups allow administrators to define reusable configuration structures that can be applied to multiple sections of the configuration. This can simplify large deployments where many interfaces or services require similar settings. Instead of duplicating the same statements repeatedly, administrators can place common settings into a configuration group and inherit or apply them where appropriate. Routing instances separate routing environments, firewall policers control traffic rates, and forwarding classes are associated with traffic classification and CoS behavior. Configuration groups therefore provide a practical method for reducing configuration duplication and improving consistency across similar device components.

Question 250

Which IPv6 mechanism allows hosts to configure addresses automatically?

1. SLAAC
2. DHCP relay
3. ARP
4. BOOTP

Correct Answer: 1

Explanation:

Stateless Address Autoconfiguration, or SLAAC, allows IPv6 hosts to automatically configure addresses using information learned through IPv6 Neighbor Discovery. Router Advertisements can provide network-prefix information that hosts use to construct their own addresses. This reduces the need for a central server to assign every individual address. DHCPv6 can provide additional or stateful configuration when required, but SLAAC itself is designed around stateless host address generation. ARP is an IPv4 mechanism and is not used by IPv6, while BOOTP is an older configuration protocol. SLAAC is therefore a key IPv6 mechanism for automatic address configuration.

Question 251

Which Junos component contains packet forwarding lookup information?

1. Routing Engine database
2. Forwarding table
3. Candidate configuration
4. Syslog archive

Correct Answer: 2

Explanation:

The forwarding table contains information used by the forwarding plane to make packet-forwarding decisions. Routes selected by the control plane are translated into forwarding information that can be used by the Packet Forwarding Engine. This allows packets to be processed efficiently without requiring a complete routing-protocol calculation for every packet. The Routing Engine maintains control-plane information, while the candidate configuration contains proposed configuration changes. Syslog archives contain event messages and do not determine packet forwarding. Understanding the forwarding table is important when troubleshooting situations where a route exists in the routing table but forwarding behavior does not appear as expected.

Question 252

Which BGP feature exchanges routing information for multiple address families?

1. Multiprotocol BGP
2. Route Damping
3. Cluster Reflection
4. AS Path Prepending

Correct Answer: 1

Explanation:

Multiprotocol BGP, commonly called MP-BGP, extends BGP so that it can carry routing information for multiple network-layer address families. This capability is important for technologies such as IPv6 routing and Layer 3 VPN services, where BGP must exchange information beyond traditional IPv4 unicast routes. MP-BGP uses capability negotiation so neighboring speakers can determine which address families they support. Route Damping addresses unstable routes, cluster-related mechanisms support route reflection, and AS Path Prepending influences path selection by modifying AS-path information. MP-BGP is therefore specifically associated with carrying multiple types of network-layer reachability information.

Question 253

Which Junos command displays detailed information about installed interfaces?

1. show interfaces extensive
2. show interfaces terse
3. show interfaces descriptions
4. show interfaces diagnostics optics

Correct Answer: 1

Explanation:

The show interfaces extensive command provides detailed operational information about interfaces. Depending on the interface and platform, the output can include administrative and operational status, traffic counters, errors, protocol information, physical properties, and other diagnostic details. This makes it useful when a simple interface summary is not sufficient to diagnose a connectivity or performance problem. The terse command provides a compact overview, descriptions emphasize configured interface descriptions, and optical diagnostics focus on transceiver information. When engineers need comprehensive interface-level operational details, the extensive command is generally the more appropriate diagnostic choice.

Question 254

Which BGP attribute carries policy classification information between routers?

1. Community
2. Origin
3. MED
4. Aggregator

Correct Answer: 1

Explanation:

The BGP Community attribute allows routes to be tagged with policy-related classification information. Administrators can use communities to group routes according to characteristics such as customer type, geographic region, service class, or desired routing treatment. Routing policies can then match those community values and apply appropriate actions. Communities provide a flexible way to communicate policy intent without relying exclusively on individual prefixes. The Origin attribute describes route origin, MED can influence certain inter-AS path decisions, and Aggregator provides information associated with route aggregation. Communities are therefore particularly useful for scalable BGP policy implementation.

Question 255

Which Junos technology supports centralized device configuration through models?

1. NETCONF
2. Telnet
3. Console
4. FTP

Correct Answer: 1

Explanation:

NETCONF is a network management protocol designed for structured configuration and operational data exchange. In Junos environments, NETCONF can work with YANG-based models to provide programmatic access to configuration and state information. This makes it suitable for automation systems that need predictable, structured interactions with network devices. Telnet and console access are primarily interactive management methods, while FTP is intended for file transfer. NETCONF can help automation tools modify configuration consistently without depending entirely on screen-oriented CLI interaction. It is therefore an important technology in model-driven network management and automated Junos administration.

Question 256

Which Layer 2 feature prevents unauthorized devices becoming spanning-tree roots?

1. Root protection
2. DHCP snooping
3. Port mirroring
4. MACsec

Correct Answer: 1

Explanation:

Root protection is a spanning-tree security mechanism that helps prevent an unexpected switch from becoming a superior spanning-tree root through a protected interface. It is typically applied where the administrator knows that a particular interface should not receive superior BPDUs that could influence root selection. If such BPDUs are detected, the protection mechanism can place the interface into an appropriate state rather than allowing the topology to change normally. DHCP snooping protects DHCP behavior, port mirroring provides traffic visibility, and MACsec protects Ethernet frames. Root protection specifically addresses unwanted changes to spanning-tree root placement.

Question 257

Which protocol synchronizes clocks across network infrastructure devices?

1. NTP
2. LDAP
3. RADIUS
4. TFTP

Correct Answer: 1

Explanation:

Network Time Protocol, or NTP, synchronizes system clocks across networked devices. Accurate time is important for many operational functions, including log correlation, troubleshooting, authentication mechanisms, certificates, and event analysis. NTP uses a hierarchy of time sources so devices can obtain time from reliable upstream references. LDAP provides directory-related services, RADIUS supports centralized authentication and authorization, and TFTP provides basic file transfer. NTP therefore serves the specific purpose of maintaining consistent time across network infrastructure. Accurate clock synchronization becomes especially important when administrators need to compare events occurring on multiple devices.

Question 258

Which Junos capability enables scheduled configuration activation?

1. commit at
2. commit check
3. commit confirmed
4. commit synchronize

Correct Answer: 1

Explanation:

The Junos commit at capability allows a configuration commit to be scheduled for a specified future time. This can be useful when administrators want changes to become active during a planned maintenance window rather than immediately. The candidate configuration can be prepared and then scheduled for activation according to the chosen time. commit check only validates the configuration, commit confirmed provides temporary rollback protection requiring confirmation, and commit synchronize addresses synchronization in supported multi-routing-engine environments. Scheduled commits therefore provide a mechanism for controlling when a prepared configuration becomes active.

Question 259

Which multicast protocol supports IPv4 receiver membership reporting?

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

Correct Answer: 1

Explanation:

IGMP is used by IPv4 hosts to communicate multicast group membership information to directly connected multicast routers. A host can indicate that it wants to receive traffic for a particular multicast group, and routers can use that information when determining whether multicast traffic should be forwarded onto the local segment. PIM is responsible for multicast routing between routers, while MSDP can exchange source information between multicast domains. MLD provides similar membership functionality for IPv6 rather than IPv4. IGMP is therefore the appropriate protocol when discussing IPv4 multicast receiver membership and reporting.

Question 260

Which Junos mechanism applies common settings to multiple configuration sections?

1. Configuration groups
2. Route targets
3. Routing policies
4. Forwarding classes

Correct Answer: 1

Explanation:

Junos configuration groups allow administrators to define common configuration statements once and reuse them across multiple configuration sections. This is particularly helpful in environments where many interfaces or services share similar settings. Using groups can reduce repetitive configuration and make large configurations easier to maintain. When common parameters need to change, administrators can update the group rather than manually editing every repeated section. Route targets are used with VPN-related routing policies, routing policies control route processing, and forwarding classes support traffic classification. Configuration groups are therefore specifically designed to promote reusable and consistent Junos configuration.