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Question 61:

Which Junos feature allows multiple physical interfaces to operate as a single logical interface for increased bandwidth and redundancy?

1. VLAN
2. LACP
3. VRRP
4. STP

Correct Answer: 2

Explanation:

LACP, or Link Aggregation Control Protocol, allows multiple physical Ethernet links to be combined into a single logical aggregated interface. This provides increased bandwidth and redundancy because traffic can use multiple physical links while the logical connection remains available if one member fails. LACP dynamically negotiates the aggregation relationship between compatible devices. VLANs provide Layer 2 segmentation, VRRP provides gateway redundancy, and STP prevents Layer 2 loops. Link aggregation is particularly useful for switch-to-switch and switch-to-server connections that require higher availability and throughput.

Question 62:

Which Junos command displays detailed information about a specific interface, including statistics and physical characteristics?

1. show interfaces extensive
2. show route
3. show arp
4. show configuration

Correct Answer: 1

Explanation:

The show interfaces extensive command provides detailed information about an interface, including its operational state, administrative state, physical characteristics, counters, errors, and traffic statistics. It is useful when troubleshooting interface problems such as packet errors, link failures, or unexpected traffic behavior. The show interfaces terse command provides a shorter summary, while show route displays routing information. show arp provides address-resolution information, and show configuration displays configured statements. Detailed interface information can help determine whether a problem originates at the physical, data-link, or logical interface level.

Question 63:

Which protocol is commonly used to securely transfer files between a network administrator’s computer and a Junos device?

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

Correct Answer: 3

Explanation:

Secure Copy Protocol (SCP) provides encrypted file transfers between systems using SSH. It is commonly used to transfer Junos software packages, configuration files, logs, or other files securely between an administrator’s computer and a Junos device. TFTP and traditional FTP do not provide the same level of secure transport by default. Telnet is an interactive remote-access protocol rather than a dedicated secure file-transfer mechanism. SCP is therefore a preferred option when files need to be transferred securely during network administration or device maintenance.

Question 64:

Which Junos feature allows an administrator to save a configuration state before making potentially risky changes?

1. Rollback
2. Commit confirmed
3. VLAN tagging
4. Route reflection

Correct Answer: 2

Explanation:

The commit confirmed feature provides a safety mechanism when making configuration changes remotely. It activates the new configuration but requires the administrator to confirm the change within a specified period. If confirmation is not received, Junos automatically rolls back to the previous configuration. This is especially valuable when making changes that could accidentally disrupt management connectivity. The rollback mechanism can also restore earlier configurations, but commit confirmed specifically protects against being locked out by an untested configuration change. It is an important operational safety feature in Junos environments.

Question 65:

Which Junos command displays the configured and learned ARP entries for IPv4 neighbors?

1. show ethernet-switching table
2. show arp
3. show route
4. show bgp summary

Correct Answer: 2

Explanation:

The show arp command displays Address Resolution Protocol information for IPv4 neighbors. ARP maps IPv4 addresses to corresponding Layer 2 MAC addresses on directly connected networks. This information is useful when troubleshooting local IPv4 connectivity problems, especially when a device can reach the network but cannot communicate with a specific neighboring host. The Ethernet switching table contains Layer 2 MAC-learning information, while the routing table contains Layer 3 routes. BGP summary information focuses on BGP peer sessions. Checking ARP can help determine whether address resolution is functioning correctly.

Question 66:

Which Junos command can display the current system uptime and the time since the device was last rebooted?

1. show system uptime
2. show chassis hardware
3. show system users
4. show route

Correct Answer: 1

Explanation:

The show system uptime command provides information about how long a Junos device has been running and when it was last booted. This information can be useful during troubleshooting because unexpected reboots, crashes, or power interruptions may explain recent network disruptions. The command can also provide information about system uptime and related timing details. show chassis hardware focuses on installed hardware, show system users displays logged-in users, and show route provides routing information. System uptime is a useful first check when investigating unexplained device restarts.

Question 67:

Which routing protocol uses a hop-count metric and has a maximum usable hop count of 15?

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

Correct Answer: 3

Explanation:

Routing Information Protocol (RIP) uses hop count as its routing metric. A maximum metric of 15 is considered reachable, while a metric of 16 represents an unreachable destination. This limitation makes RIP unsuitable for many large modern networks. OSPF and IS-IS use link-state algorithms with more sophisticated path calculations, while BGP uses a path-vector model and multiple attributes. RIP can still be encountered in legacy environments, but its limited scalability and relatively slow convergence mean that modern enterprise and service-provider networks generally use more advanced routing protocols.

Question 68:

Which BGP attribute is used to identify the next-hop router that should be used to reach a destination?

1. Community
2. Next hop
3. Local preference
4. MED

Correct Answer: 2

Explanation:

The BGP Next Hop attribute identifies the IP address that should be used as the next-hop toward a destination advertised through BGP. Correct next-hop information is essential for successful forwarding because a route can be present in the routing table while still being unusable if its next hop cannot be resolved. In some designs, the next-hop self policy is used to modify the next-hop address when advertising routes to another BGP peer. Local preference and MED influence path selection, while communities provide policy tags.

Question 69:

Which Junos mechanism can modify the DSCP value of packets to provide different treatment for traffic classes?

1. Routing policy
2. Rewrite rule
3. Routing instance
4. Static route

Correct Answer: 2

Explanation:

A CoS rewrite rule can modify packet classification markings such as DSCP. This allows a Junos device to change the markings carried in packets as they leave an interface or move between network domains. Rewriting can be useful when different network segments use different traffic-classification policies or when traffic needs to be remarked before entering another network. Routing policies manipulate routing information, routing instances provide routing separation, and static routes specify manually configured forwarding paths. Rewrite rules are therefore an important component of Junos Class of Service implementations.

Question 70:

Which Junos command can be used to view the current active configuration without entering configuration mode?

1. show route
2. show configuration
3. show interfaces terse
4. show system uptime

Correct Answer: 2

Explanation:

The show configuration command can be used from operational mode to display the active configuration hierarchy. This allows administrators to inspect configuration statements without entering configuration mode. Reviewing the configuration is useful when verifying interface settings, routing protocols, policies, security settings, and other device parameters. show route displays routing information, show interfaces terse provides interface status, and show system uptime provides system runtime information. The ability to inspect the configuration directly from operational mode is an important part of routine Junos administration and troubleshooting.

Question 71:

Which technology is commonly used to provide secure Layer 3 VPN services across an MPLS provider network?

1. MPLS Layer 3 VPN
2. STP
3. LLDP
4. LACP

Correct Answer: 1

Explanation:

MPLS Layer 3 VPNs allow service providers to carry customer IP traffic across a shared MPLS infrastructure while maintaining logical separation between customers. Customer routes are typically maintained in separate VRF routing instances on provider edge devices. MPLS provides label-based forwarding through the provider network, while technologies such as MP-BGP can distribute VPN routing information between provider edge devices. STP is used for Layer 2 loop prevention, LLDP provides neighbor discovery, and LACP provides link aggregation. MPLS Layer 3 VPNs are widely used for scalable managed WAN services.

Question 72:

What is the main purpose of a VRF routing table?

1. Store only MAC addresses
2. Separate routing information for different logical networks
3. Provide packet encryption
4. Synchronize device clocks

Correct Answer: 2

Explanation:

A Virtual Routing and Forwarding (VRF) routing table provides logical separation of routing information on the same physical device. Different customers, departments, or network services can maintain independent routing tables and overlapping IP address spaces without interfering with one another. This is particularly important in service-provider networks and enterprise segmentation designs. VRF does not inherently encrypt packets, synchronize clocks, or function as a MAC address database. In Junos, routing instances can be used to implement VRF functionality and associate interfaces and routes with specific logical routing environments.

Question 73:

Which BGP attribute can be used to attach policy information to a group of routes without changing the routes themselves?

1. Community
2. AS path
3. Next hop
4. Origin

Correct Answer: 1

Explanation:

BGP communities allow administrators to attach policy-related information to routes. A route can be tagged with one or more communities, and routing policies can then match those tags and apply appropriate actions. This makes communities useful for implementing scalable routing policies without needing to create individual policies for every prefix. AS path records the autonomous systems through which a route has traveled, next hop identifies forwarding information, and origin describes how the route entered BGP. Communities are therefore a powerful mechanism for organizing and controlling BGP route behavior.

Question 74:

Which Junos feature allows administrators to automatically revert a configuration change if the device loses connectivity after the change?

1. Commit confirmed
2. LACP
3. RSTP
4. Route reflector

Correct Answer: 1

Explanation:

commit confirmed is specifically designed to protect against configuration changes that unintentionally disrupt connectivity. When an administrator commits a configuration using this mechanism, Junos starts a confirmation timer. The administrator must issue another commit to confirm the configuration before the timer expires. If confirmation does not occur, Junos automatically returns to the previous committed configuration. This is particularly useful when working remotely because a configuration error could otherwise leave the administrator unable to reconnect. LACP, RSTP, and route reflection provide completely different networking functions.

Question 75:

Which protocol is commonly used to collect network-device monitoring information such as interface counters and system statistics?

1. SNMP
2. NTP
3. SCP
4. SSH

Correct Answer: 1

Explanation:

Simple Network Management Protocol (SNMP) is widely used for monitoring network devices and collecting information such as interface statistics, system health, and operational counters. Network management systems can poll devices using SNMP and may also receive asynchronous notifications such as traps. NTP synchronizes system clocks, SCP securely transfers files, and SSH provides secure remote administration. SNMP does not replace logging or configuration management, but it is an important component of network monitoring. Proper security controls should be applied when deploying SNMP, especially with older versions that provide weaker security.

Question 76:

Which logging facility can be configured on Junos to send system messages to a remote log server?

1. Syslog
2. ARP
3. OSPF
4. LACP

Correct Answer: 1

Explanation:

Syslog provides a standard mechanism for collecting and forwarding system and event messages. Junos can be configured to send selected log messages to a remote syslog server, allowing administrators to centralize logs from multiple network devices. Centralized logging improves troubleshooting, monitoring, and security analysis because events can be reviewed from a common location. ARP resolves IPv4 addresses to MAC addresses, OSPF exchanges routing information, and LACP manages link aggregation. Syslog is therefore the appropriate technology for centralized collection of Junos system messages.

Question 77:

Which Junos command is useful for viewing recently generated system log messages?

1. show log messages
2. show route
3. show arp
4. show chassis hardware

Correct Answer: 1

Explanation:

The show log messages command can be used to examine messages recorded in the Junos system log file named messages. These logs can contain information about interface changes, routing events, system errors, authentication activity, and other operational conditions depending on the configured logging policy. Reviewing logs is an important troubleshooting technique because they can reveal events that are not immediately visible through interface or routing commands. The other commands provide routing, ARP, and hardware information rather than system log contents.

Question 78:

Which mechanism allows a Junos administrator to test a configuration before committing it?

1. commit check
2. rollback 0
3. show route
4. deactivate

Correct Answer: 1

Explanation:

The commit check command validates the candidate configuration without activating the changes. It allows Junos to identify configuration syntax or consistency problems before the administrator performs a normal commit. This is particularly useful when making multiple changes or modifying complex services. A successful commit check does not mean that the configuration has been activated; the administrator still needs to issue commit to apply it. Rollback is used to return toward earlier configurations, while show route and deactivate serve different operational and configuration purposes.

Question 79:

Which routing protocol is considered a link-state protocol and supports hierarchical routing through areas?

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

Correct Answer: 3

Explanation:

OSPF is a link-state routing protocol that supports hierarchical network designs using areas. Area 0, known as the backbone area, provides the central inter-area connectivity in a traditional OSPF architecture. Routers exchange link-state information and maintain a link-state database from which the SPF algorithm calculates routes. BGP is a path-vector protocol, RIP is a distance-vector protocol, and VRRP provides gateway redundancy rather than routing-domain path calculation. OSPF areas help control the size of the link-state database and reduce routing overhead in larger networks.

Question 80:

Which Junos feature is used to control which routes are accepted from or advertised to a routing protocol neighbor?

1. Firewall filter
2. Routing policy
3. CoS scheduler
4. VLAN

Correct Answer: 2

Explanation:

Routing policies control how routes are imported, exported, accepted, rejected, or modified. They can be applied to routing protocols such as BGP and can match information including prefixes, communities, AS paths, and protocol attributes. For example, an administrator can create a policy that accepts only specific prefixes from a BGP neighbor or modifies the local preference of selected routes. Firewall filters operate on packets, CoS schedulers control traffic transmission, and VLANs provide Layer 2 segmentation. Routing policies are therefore fundamental for controlling route exchange and implementing routing decisions in Junos.