JN0-106 Practice Test 5 — 10 Questions

Question 1

During a maintenance window, an engineer issues 'commit confirmed 5' but the change causes a connectivity loss. The engineer is unable to reconnect to the device before the timeout expires. What will happen?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

The device automatically reverts to the previous active configuration.. The 'commit confirmed 5' command activates a candidate configuration and starts a 5-minute rollback timer. If the engineer does not issue a 'commit' or 'commit check' before the timer expires, Junos automatically reverts to the previously active configuration. This ensures the device returns to a known working state without manual intervention, preserving connectivity after the failed change.

Answer

The engineer must manually rollback using the rollback command.

Answer

The change remains committed until the next reboot.

Answer

The device reloads with factory defaults.

Question 2

A network operator needs to backup the current configuration to a file on the local flash. Which command accomplishes this?

Accepted Answer

show configuration | save /var/tmp/backup.conf. The correct command to backup the current configuration from operational mode is `show configuration | save /var/tmp/backup.conf`. This pipes the active configuration to the save command, writing it to the specified file. Option B (`save /var/tmp/backup.conf`) is a configuration mode command and will not work in operational mode. Option A saves the rescue configuration, not the active configuration. Option C commits the configuration and exits but does not save to a file.

Answer

request system configuration rescue save

Answer

save /var/tmp/backup.conf

Answer

commit and-quit

Question 3

A Junos device has multiple configuration files saved. Which command shows the available rollback configurations?

Accepted Answer

show system commit. The 'show system commit' command displays a list of all committed configuration revisions, including their commit IDs and timestamps, which are used to roll back to a previous configuration. The rollback feature in Junos relies on these stored commit files, and the command explicitly shows the available rollback points.

Answer

show system configuration

Answer

show system rollback

Answer

show configuration | display rollback

Question 4

A technician needs to view the last 50 log messages from the system log file. Which command accomplishes this?

Accepted Answer

show log messages | last 50. The 'show log messages | last 50' command displays the last 50 lines from the /var/log/messages file on a Junos device. The pipe to 'last' is a Junos CLI filter that outputs only the final N lines of the command output, which is exactly what is needed to view the most recent log entries.

Answer

show system log messages

Answer

monitor start messages

Answer

show system syslog

Question 5

You are a network administrator for a large enterprise. You have a Juniper SRX firewall that is used as the primary internet gateway. Users are reporting that they are unable to access certain external websites. You check the device and find that the security policies appear correct, and the routing is in place. You suspect that the issue might be related to the DNS resolution. You want to verify that the device can resolve DNS names and that the DNS server configuration is correct. Which command should you use to test DNS resolution from the Juniper device?

Accepted Answer

ping <external website FQDN>. The `ping` command with a fully qualified domain name (FQDN) forces the Juniper device to perform a DNS resolution before sending ICMP echo requests. If the device cannot resolve the FQDN, the ping will fail with a 'hostname not found' error, directly indicating a DNS configuration or reachability issue. This tests both the DNS server configuration and the device's ability to resolve names, which is essential for verifying DNS functionality.

Answer

show system connections

Answer

traceroute <external website FQDN>

Answer

show dns name-server

Question 6

A network administrator wants to see the current CPU load average over the last 1, 5, and 15 minutes on a Juniper device. Which command displays this information?

Accepted Answer

show system uptime. The 'show system uptime' command displays the system's uptime along with the load averages for the last 1, 5, and 15 minutes. This is the standard Junos command for viewing CPU load averages, which are calculated based on the number of processes in the run queue over those time intervals.

Answer

show chassis routing-engine

Answer

show system processes

Answer

show system statistics

Question 7

Your data center uses Juniper QFX5110 switches as leaf nodes in a Virtual Chassis Fabric (VCF) topology with QFX5100 as spine nodes. You are adding a new QFX5110 leaf node to the fabric. The new switch is physically connected to all spine nodes as per the cabling guidelines. However, after powering on the new switch, it does not automatically join the fabric. The existing fabric shows the new switch's member ID as 8, but it remains in 'standalone' state. The VCF has been operational for several months without issues. You check the configuration on the existing VC and notice that the 'virtual-chassis' configuration does not include the new member. What is the most likely reason the new switch does not join?

Accepted Answer

The new switch does not have the same virtual-chassis ID configured as the existing fabric. In a Virtual Chassis Fabric (VCF), all member switches must share the same virtual-chassis ID to be recognized as part of the same fabric. The existing fabric has a configured virtual-chassis ID, but the new QFX5110, by default, has a different or no virtual-chassis ID set. Without a matching virtual-chassis ID, the new switch cannot join the fabric and remains in 'standalone' state, even though it is physically connected and assigned a member ID.

Answer

The new switch is running a different version of Junos that is not compatible with the fabric

Answer

The new switch is only connected to one spine node, and VCF requires full mesh connections to all spines

Answer

The new switch has 'set virtual-chassis no-split-detection' enabled, preventing it from joining

Question 8

A router has two ISIS adjacencies to the same router, both with equal metrics. The router installs both routes in the routing table and performs load balancing. The network team wants to verify that both next-hops are being used for a particular destination. Which command provides this information?

Accepted Answer

`show route forwarding-table destination 10.0.0.0/24`. The `show route forwarding-table destination 10.0.0.0/24` command displays the actual forwarding entries in the Packet Forwarding Engine (PFE), including all next-hops used for load balancing. Unlike the routing table, the forwarding table shows which next-hops are actively installed and used for forwarding traffic, making it the definitive command to verify equal-cost multipath (ECMP) usage.

Answer

`show route 10.0.0.0/24 extensive`

Answer

`show route protocol isis`

Answer

`show route 10.0.0.0/24 detail`

Question 9

A network engineer is troubleshooting connectivity between two directly connected Juniper routers. The interface on Router A shows 'up' but no packets are being received from Router B. Which command should the engineer use on Router A to check if the interface is expecting to receive a specific encapsulation type?

Accepted Answer

show interfaces extensive. The 'show interfaces extensive' command displays detailed interface information, including the encapsulation type configured on the interface. If Router A expects a specific encapsulation (e.g., PPP, HDLC, or Ethernet) that does not match what Router B is sending, the interface will show 'up' but will not receive packets. This command allows the engineer to verify the configured encapsulation type. Option B is incorrect because 'show interfaces terse' provides a concise summary (name, status, protocol, and address) but does not include encapsulation details.

Answer

show interfaces terse

Answer

show configuration interfaces

Answer

monitor traffic interface

Question 10

You are managing a Juniper MX240 router at a small ISP. The router has been operating normally for months. This morning, a customer reports intermittent packet loss on their connection, which is served by interface ge-0/0/2. You SSH into the router and run 'show interfaces ge-0/0/2 extensive'. The output shows input errors increasing rapidly, including CRC errors and frame errors. The interface is up/up. You also notice that the interface statistics show a high number of carrier transitions. The cable connecting the router to the customer's CPE was recently replaced by the customer's technician. What is the most likely cause of the errors and the correct action to resolve the issue?

Accepted Answer

Replace the cable with a known good one because CRC and frame errors indicate a physical layer problem such as a damaged cable or loose connector.. CRC and frame errors increasing rapidly, combined with a high number of carrier transitions, are classic symptoms of a physical-layer issue. Since the cable was recently replaced by the customer's technician, the most likely cause is a faulty cable or a loose connector. Replacing the cable with a known good one directly addresses the physical layer problem, which is the root cause of these errors.

Answer

Clear the MAC address table on the router to fix possible MAC flapping issues.

Answer

Administer a 'shutdown' and 'no shutdown' on the interface to reset the line protocol.

Answer

Change the interface speed and duplex settings to auto-negotiate because the errors are due to a mismatch between the router and CPE.