JN0-106 Operational Monitoring and Maintenance — Timed 50 Questions

Question 1

After a software upgrade, BGP sessions are not establishing. The engineer runs 'show bgp summary' and sees that all sessions are in Idle state. What is the most likely cause?

Accepted Answer

The BGP group configuration is missing. The Idle state in BGP indicates that the session has not started the connection process, often because the BGP configuration is incomplete or missing. If the BGP group configuration is missing, the router has no peers to initiate sessions with, so all sessions remain in Idle. This is the most likely cause when all sessions are in Idle after a software upgrade, as configuration elements may be lost or not applied.

Answer

The interface is administratively down

Answer

The router has a full BGP table

Answer

The firewall filter is blocking ICMP

Question 2

Which THREE statements are true about the 'show interfaces ge-0/0/0 extensive' command output?

Accepted Answer

It displays a detailed count of errors. The 'show interfaces ge-0/0/0 extensive' command provides a comprehensive view of the interface. It displays detailed error counters (e.g., CRC, frame errors), traffic statistics (e.g., bytes, packets), and the administrative status (e.g., 'Up' or 'Down'). Options A, C, and E are true statements about the output.

Answer

It includes only layer 1 information

Answer

It shows the interface configuration

Question 3

Which THREE commands are used for operational monitoring of routing protocols?

Accepted Answer

show isis adjacency. The 'show isis adjacency' command is used to verify the state of IS-IS neighbor adjacencies, which is a core operational monitoring task for the IS-IS routing protocol. It displays the interface, neighbor system ID, level, and adjacency state (e.g., Up, Down, Initializing), allowing an engineer to confirm that IS-IS neighbors are properly established.

Answer

show interfaces terse

Answer

show arp

Question 4

Which TWO statements are correct about the 'monitor interface' command?

Accepted Answer

It displays output in real-time. The 'monitor interface' command in Junos OS displays real-time statistics for the specified interface, updating continuously until the user terminates it. This is why option A is correct: it provides a live, dynamic view of interface counters like packets, errors, and bandwidth utilization.

Answer

It shows a static snapshot

Answer

It requires a 'start' parameter

Answer

It provides historical statistics

Question 5

You are managing a Juniper MX router that serves as a BGP route reflector for multiple customer VPNs. The router has two routing engines (RE0 and RE1) in a graceful switchover (GRES) configuration. During a routine maintenance window, you need to upgrade the Junos OS from version 18.1R1 to 20.2R2. The upgrade must minimize traffic disruption. You have already staged the new image on both REs. Which sequence of commands ensures minimal impact?

Accepted Answer

On RE1: request system software add jinstall-20.2R2.tgz reboot; after reboot, on RE0: request chassis routing-engine master switch; then request system software add jinstall-20.2R2.tgz reboot. It performs a non-disruptive upgrade by first upgrading the backup RE (RE1), then switching mastership to the upgraded RE, and finally upgrading the original master RE. This sequence leverages Graceful Routing Engine Switchover (GRES) to maintain BGP sessions and VPN forwarding during the upgrade, minimizing traffic disruption.

Answer

On RE0: request system software add jinstall-20.2R2.tgz reboot; then on RE1 same command

Answer

On RE0: request system reboot (without adding software)

Answer

On both REs: request system software add jinstall-20.2R2.tgz reboot

Question 6

Which THREE statements about the 'request system snapshot' command are true? (Choose three.)

Accepted Answer

It creates a recovery media for the device.. The 'request system snapshot' command creates a bootable recovery media (e.g., USB or compact flash) that contains a copy of the current Junos OS and configuration. This allows the device to boot from that media in case of a system failure, effectively serving as a recovery tool.

Answer

It compresses the backup to save space.

Answer

It copies the active partition to the alternate partition on the same media.

Question 7

Based on the exhibit, which protocol is enabled on interface ge-0/0/0.0?

Accepted Answer

MPLS. The exhibit shows that interface ge-0/0/0.0 has the 'family mpls' statement configured under it, which enables MPLS on that interface. MPLS is explicitly enabled at the protocol family level, allowing the interface to participate in MPLS label switching.

Answer

IS-IS

Answer

BGP

Answer

OSPF

Question 8

You are the network administrator for a large enterprise with a Juniper MX480 router running Junos 18.2R3. The router has two Routing Engines (RE0 and RE1) in a graceful Routing Engine switchover (GRES) configuration. During a scheduled maintenance window, you need to upgrade the Junos OS to a newer version while minimizing traffic loss. The upgrade process requires a reboot of both REs. You have staged the software on both REs. Which sequence of commands should you use to perform the upgrade with minimal disruption?

Accepted Answer

On RE1 (backup): request system software add re1; request system reboot re1. After reboot, request chassis routing-engine master switch. On RE0 (now backup): request system software add re0; request system reboot re0.. It performs a hitless upgrade by first upgrading and rebooting the backup RE (RE1), then performing a graceful mastership switch using 'request chassis routing-engine master switch', and finally upgrading and rebooting the former primary (now backup) RE0. This sequence ensures that during each RE reboot, the other RE remains active and continues forwarding traffic, leveraging GRES to maintain state and minimize packet loss.

Answer

On both REs: request system software add <image>; then request system reboot both REs simultaneously.

Answer

On RE0: request system software add re0; on RE1: request system software add re1; then request system reboot both.

Answer

On RE0 (primary): request system software add re0; request system reboot re0. After reboot, on RE1: request system software add re1; request system reboot re1.

Question 9

Which THREE statements correctly describe the use of the 'monitor traffic' command in Junos?

Accepted Answer

It can filter packets using the 'matching' option to capture only specific traffic.. The 'monitor traffic' command supports a 'matching' option that allows you to specify a BPF filter to capture only specific traffic. Option C is correct because 'monitor traffic interface ' captures packets on a specific interface and displays them in real-time. Option E is correct because the 'monitor traffic' command can read packets from a previously saved pcap file using the 'file' option (e.g., 'monitor traffic file '), which is useful for offline analysis.

Answer

It captures packets from the Routing Engine only.

Answer

It requires a reboot to start capturing packets.

Question 10

Refer to the exhibit. A network engineer sees repeated 'PFE interrupt error' messages in the log for fpc0. What is the most likely impact and recommended action?

Accepted Answer

Replace the line card (FPC0) as it is experiencing hardware failures causing traffic loss.. The 'PFE interrupt error' message indicates a hardware-level failure on the Packet Forwarding Engine (PFE) of FPC0. Since the PFE is responsible for forwarding packets, such errors typically cause traffic loss or drops. The recommended action is to replace the line card (FPC0) because persistent PFE interrupt errors are symptomatic of a hardware fault that cannot be resolved by software resets or upgrades.

Answer

Remove and reinsert the PIC on FPC0 to reseat the connection.

Answer

Restart the PFE process using 'restart pfe' command.

Answer

Perform a software upgrade on the router to fix a known bug.

Question 11

Arrange the steps to configure OSPF on a Junos router in the correct order.

Accepted Answer

Step 1: Configure the router ID. Step 2: Configure the OSPF area and assign interfaces. Step 3: Verify OSPF neighbor relationships.. OSPF requires a router ID and interfaces assigned to areas. Verification shows neighbor relationships.

Answer

Step 1: Configure the OSPF area and assign interfaces. Step 2: Configure the router ID. Step 3: Verify OSPF neighbor relationships.

Answer

Step 1: Verify OSPF neighbor relationships. Step 2: Configure the router ID. Step 3: Configure the OSPF area and assign interfaces.

Answer

Step 1: Configure the router ID. Step 2: Verify OSPF neighbor relationships. Step 3: Configure the OSPF area and assign interfaces.

Question 12

Arrange the steps to configure a DHCP server on a Junos router.

Accepted Answer

Step 1: Enable DHCP services. Step 2: Configure a DHCP pool with subnet and range. Step 3: Set DHCP options (gateway, DNS). Step 4: Exclude specific addresses.. The correct sequence for configuring a DHCP server on a Junos router is to first enable DHCP services, then define a pool with subnet and range, set DHCP options like gateway and DNS, and finally exclude specific addresses. This ensures all dependencies are met and the configuration is applied logically.

Answer

Step 1: Configure a DHCP pool with subnet and range. Step 2: Enable DHCP services. Step 3: Set DHCP options. Step 4: Exclude specific addresses.

Answer

Step 1: Enable DHCP services. Step 2: Set DHCP options. Step 3: Configure a DHCP pool with subnet and range. Step 4: Exclude specific addresses.

Answer

Step 1: Enable DHCP services. Step 2: Configure a DHCP pool with subnet and range. Step 3: Exclude specific addresses. Step 4: Set DHCP options.

Question 13

Match each Junos security feature to its description.

Accepted Answer

Screen: Provides protection against various types of network attacks. The correct matches are: Screen for attack protection, Zone for grouping interfaces, Security Policy for traffic rules, and NAT for address translation. Common confusions include mixing Screen with Security Policy or Zone with NAT.

Answer

Screen: Defines rules to permit or deny traffic based on source, destination, application

Answer

Zone: Translates private IP addresses to public IP addresses

Question 14

Match each Junos operational command for monitoring to its output.

Accepted Answer

show interfaces: Displays interface status and packet counts. The correct matches are: show interfaces with interface status, show route with routing table, and show log with system logs. Common confusions involve swapping outputs among these commands.

Answer

show interfaces: Displays routing table entries

Answer

show version: Displays interface status

Question 15

During a maintenance window, an engineer plans to replace a line card. Which command sequence is most appropriate to gracefully deactivate the card before removal?

Accepted Answer

request chassis pic slot offline; request chassis fpc offline. The 'request chassis fpc offline' command gracefully deactivates the Flexible PIC Concentrator (FPC) by stopping traffic, closing sessions, and powering down the line card safely. The 'request chassis pic slot offline' command is used for individual PICs, but for a full line card (FPC), the FPC-level command is the appropriate sequence to ensure no traffic disruption or hardware damage during removal.

Answer

delete interfaces fxp0

Answer

set interfaces <name> disable

Answer

request system reboot

Question 16

Refer to the exhibit. What is the most likely cause of the BGP session failure?

Accepted Answer

Hold timer expired due to delayed keepalives. The BGP session failure is most likely due to the hold timer expiring because keepalive messages were not received in time. In JUNOS, the default hold time is 90 seconds, and if a router does not receive a keepalive or update within that interval, it declares the peer dead and resets the session. The exhibit shows the BGP state as 'Idle' or 'Active', which is consistent with a hold timer expiry event.

Answer

The peer is unreachable

Answer

BGP configuration mismatch

Answer

Route flapping

Question 17

Refer to the exhibit. Which route will be used to forward traffic to 192.168.1.0/24?

Accepted Answer

The route via 10.0.0.2 because it has a lower metric. The route via 10.0.0.2 is selected because it has a lower metric. In Junos, when multiple routes to the same destination have the same preference (administrative distance), the route with the lower metric is preferred. The exhibit shows two OSPF routes with equal preference, so the metric determines the active route.

Answer

Neither route is valid

Answer

The route via 10.0.0.1 because it was learned later

Answer

Both routes are used for load balancing

Question 18

During a network outage, a router is unresponsive via SSH. You have console access but the console displays 'Amnesiac (ttyd0)' prompt. What is the most likely cause and recovery action?

Accepted Answer

The router lost its configuration; load the rescue configuration using 'rollback rescue-config' or 'load override /config/rescue.conf.gz' then commit. The 'Amnesiac (ttyd0)' prompt indicates the router has booted without a valid configuration file in the /config directory. This typically occurs after a 'request system zeroize' command, a failed commit that corrupted the configuration, or a storage issue that prevented the configuration from loading. The recovery action is to load a previously saved rescue configuration using 'rollback rescue' or 'load override /config/rescue.conf.gz' and then commit, which restores the router to a known working state.

Answer

The router's boot device failed; need to replace hardware

Answer

The router booted from backup media; run 'request system software add' to reinstall Junos

Answer

The router's flash memory is corrupted; perform a full reinstall via USB

Question 19

Which TWO commands can be used to monitor system log messages in real-time?

Accepted Answer

monitor start messages. The 'monitor start messages' command streams the contents of the /var/log/messages file in real-time, allowing you to monitor system log messages as they are generated. 'monitor start interactive-commands' (Option D) monitors logs specific to interactive CLI commands, not general system log messages, so it does not satisfy the stem. The other options ('show log messages | last 100', 'show system log messages', 'show configuration system syslog') either display historical data or configuration, not real-time system log monitoring.

Answer

show log messages | last 100

Answer

show system log messages

Answer

show configuration system syslog

Answer

monitor start interactive-commands

Question 20

Which THREE statements are true about the commit operation on Junos?

Accepted Answer

The commit operation validates the configuration before applying.. Option A is correct because the Junos commit operation runs a validation of the candidate configuration against the syntax and constraints of the device's configuration schema before it is applied, rejecting invalid configurations. Option C is correct because, once the commit succeeds, the candidate configuration is activated and becomes the active (running) configuration immediately, without requiring a reboot. Option E is correct because the 'commit check' command performs the same validation as commit without actually activating the candidate configuration, allowing an administrator to verify correctness beforehand. Option B is not among the marked correct answers, and option D is false because commit applies configuration changes live and does not require a reboot.

Answer

The commit operation can be confirmed with a time delay.

Answer

The commit operation always requires a reboot.