JN0-106 Practice Test 2 — 25 Questions

Question 1

Scenario: Your company has a Juniper MX Series router at a branch office running Junos 18.4. The device has been in production for two years with a stable configuration. Yesterday, a senior engineer made several changes to the OSPF configuration to optimize routing for a new link. They committed the changes and left for the day. This morning, the branch office experiences intermittent connectivity, and the OSPF neighbor relationships are flapping. You suspect the recent OSPF changes caused the issue. You have remote console access to the router. The goal is to restore network stability as quickly as possible while preserving the ability to re-apply the changes after troubleshooting. Which course of action should you take?

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

Accepted Answer

Use 'rollback 1' to revert to the configuration before the changes, then 'commit confirmed 10' to verify stability.. 'rollback 1' reverts the active configuration to the previous committed version (before the problematic OSPF changes), and 'commit confirmed 10' applies that rollback with a 10-minute confirmation timer. If connectivity stabilizes, the rollback becomes permanent; if not, the router automatically reverts to the previous configuration, ensuring no prolonged outage. This approach restores stability quickly while preserving the ability to later re-apply and test the OSPF changes in a controlled manner.

Answer

Use 'deactivate protocols ospf' to disable OSPF entirely and then manually re-enable pieces.

Answer

Immediately delete the OSPF configuration sections that were changed and re-add the original settings manually.

Answer

Perform a 'load factory-default' and 'commit' to reset the device to base settings, then reconfigure from backup.

Question 2

Which TWO commands can be used to view the current routing table entries for IPv4 unicast routes?

Accepted Answer

show route table inet.0. `show route table inet.0` explicitly displays the IPv4 unicast routing table (inet.0) in Junos. Option D is correct because `show route` without any filter defaults to showing all routes in the inet.0 table, which is the primary IPv4 unicast routing table.

Answer

show route protocol static

Answer

show forwarding-table

Answer

show route table inet6.0

Question 3

A company wants to implement best practice for password recovery on Juniper devices to avoid service disruption. Which of the following is the recommended method?

Accepted Answer

Boot the device into single-user mode from the console and reset the root password. Booting the device into single-user mode from the console is the standard, secure method for password recovery on Juniper devices. This process allows an administrator with physical console access to reset the root password without affecting the running configuration or causing service disruption, as the device boots with a minimal kernel and does not load the full configuration.

Answer

Perform a factory reset to default configuration

Answer

Use SNMP to modify the password field in the configuration

Answer

Contact JTAC to remotely reset the password

Question 4

You are a junior network engineer at a company that uses Juniper MX routers. You are troubleshooting a connectivity issue on a branch router. The branch router has two upstream links to the corporate network: ge-0/0/0 (10.1.1.1/30, connected to core router A) and ge-0/0/1 (10.1.1.5/30, connected to core router B). The branch router runs OSPF and has a default route learned from both upstream routers. The routing table shows two equal-cost default routes via both next hops. However, traffic from the branch to the corporate network is experiencing intermittent high latency and some packet loss. You suspect that asymmetric routing is causing issues because the return traffic is not following the same path. You want to influence the router to prefer one upstream link for all traffic to the corporate network. You have decided to adjust the OSPF metric on the branch router to make the link to core router A more preferred. You are in configuration mode on the branch router. Which single configuration change will accomplish this goal?

Accepted Answer

set protocols ospf area 0 interface ge-0/0/1 metric 200. Setting the OSPF metric on interface ge-0/0/1 to a higher value (200) increases the cost of that link, making the default route via ge-0/0/0 (which retains the default OSPF metric of 1 on a Gigabit Ethernet interface) more preferred. This influences the branch router to use the lower-cost path through core router A for all traffic to the corporate network, resolving asymmetric routing issues.

Answer

set interfaces ge-0/0/1 unit 0 family inet cost 200

Answer

set protocols ospf area 0 interface ge-0/0/1 passive

Answer

set interfaces lo0 unit 0 family inet address 10.0.0.1/32 metric 100

Question 5

An engineer enables Spanning Tree PortFast on a switch port connected to a host. Later, another switch is connected to that same port, causing a loop. What feature could have prevented this?

Accepted Answer

BPDU guard. BPDU guard is the correct answer because it disables a port configured with PortFast if a BPDU is received, preventing loops when a switch is accidentally connected. In this scenario, PortFast was enabled for a host, but connecting another switch caused BPDUs to be sent, which BPDU guard detects and shuts down the port to break the loop.

Answer

Loop guard

Answer

Root guard

Answer

UplinkFast

Question 6

A Juniper device receives several routes to the same destination prefix from different routing protocols. Which parameter is used first to select the active route?

Accepted Answer

Route preference (administrative distance). When a Juniper device receives multiple routes to the same destination prefix from different routing protocols, the route preference (also known as administrative distance) is the first tiebreaker used to select the active route. Each protocol has a default preference value (e.g., OSPF internal routes have a preference of 10, while static routes have a preference of 5), and the route with the lowest preference is chosen as active. This occurs before any metric or other path attribute is considered.

Answer

Metric

Answer

AS path length

Answer

Local preference

Question 7

A company has two Juniper routers in a high-availability cluster with dual Routing Engines. The administrator performs a commit on the primary RE. What is the effect of using the 'commit synchronize' command?

Accepted Answer

It commits the configuration on both Routing Engines simultaneously.. The 'commit synchronize' command on Juniper routers with dual Routing Engines ensures that the configuration is committed on both the primary and backup REs simultaneously. This is critical for maintaining configuration consistency in a high-availability cluster, as it prevents a split-brain scenario where the backup RE has a different active configuration than the primary. The command performs a full commit (including validation and activation) on both REs, not just a check.

Answer

It performs a commit check on both REs but does not activate the config.

Answer

It commits the configuration only on the primary RE.

Answer

It commits the configuration only on the backup RE.

Question 8

A company runs a Juniper SRX firewall cluster consisting of two nodes (node0 primary, node1 secondary). The cluster has been stable. During maintenance, you modify the configuration on node0 and commit. After the commit, the cluster status shows node1 as 'ineligible'. You suspect a configuration mismatch. What should you do to synchronize the configuration without disrupting traffic?

Accepted Answer

On the primary node, execute 'commit synchronize'.. The 'commit synchronize' command on the primary node (node0) pushes the active configuration to the secondary node (node1) and commits it on both nodes, ensuring configuration consistency without requiring a reboot or traffic disruption. In a Juniper SRX cluster, the primary node is the authoritative source for configuration synchronization, and this command is the standard method to resolve a configuration mismatch that causes a node to become 'ineligible'.

Answer

Reboot both nodes to force synchronization.

Answer

Manually copy the configuration file from primary to secondary.

Answer

On the secondary node, execute 'commit synchronize'.

Question 9

A network engineer suspects a hardware issue on an interface. Which command provides the most detailed hardware error counters, including CRC errors, framing errors, and runts?

Accepted Answer

show interfaces extensive. The 'show interfaces extensive' command provides the most detailed hardware error counters for a Junos interface, including CRC errors, framing errors, and runts. This command displays per-interface statistics at the physical layer, such as input errors, output errors, and specific error types like frame, runts, giants, and CRC errors, which are essential for diagnosing hardware issues.

Answer

show interfaces diagnostics optics

Answer

show interfaces detail

Answer

show log messages

Question 10

A router receives a packet with destination IP 10.1.1.100. The routing table contains two entries: a static route to 10.1.1.0/24 via 192.168.1.1, and an OSPF route to 10.1.1.0/25 via 192.168.2.1. Which route will the router use?

Accepted Answer

The OSPF route to 10.1.1.0/25. The router will use the OSPF route to 10.1.1.0/25 because it has a longer prefix length (/25) than the static route (/24). Juniper Junos uses the most specific (longest) prefix match in the routing table, regardless of administrative distance or protocol preference. The destination IP 10.1.1.100 falls within the 10.1.1.0/25 range (10.1.1.0–10.1.1.127), so the /25 route is more specific and thus preferred.

Answer

The router drops the packet due to a routing conflict

Answer

The static route to 10.1.1.0/24

Answer

Both routes are used for load balancing

Question 11

Refer to the exhibit. A host connected to ge-0/0/1 cannot reach a host connected to ge-0/0/2 even though both are in VLAN10. What is the most likely cause?

Accepted Answer

The hosts are configured with IP addresses on different subnets.. Although both hosts are in the same VLAN and can communicate at Layer 2 (MAC addresses), IP communication requires them to be on the same IP subnet. If the hosts have IP addresses on different subnets, they will attempt to use a default gateway for routing. Without a router or IRB interface configured, the traffic cannot be delivered, leading to unreachability.

Answer

VLAN10 is not defined in the global VLAN configuration.

Answer

An IRB interface for VLAN10 is not configured.

Answer

The interface ge-0/0/2 is configured as a trunk port.

Question 12

Refer to the exhibit. What is the most likely cause of the error?

Accepted Answer

The policy-statement 'test' contains a syntax error in the protocol match condition.. The error message in the exhibit indicates a syntax error in the policy-statement 'test' when using the protocol match condition. In Junos, the 'protocol' match condition requires a valid protocol name (e.g., 'bgp', 'ospf', 'static'), and if an invalid or misspelled protocol is specified, the commit check fails with a syntax error. This is a common mistake when configuring policy-options, as the Junos CLI validates the protocol against a predefined list.

Answer

The IP address 1.1.1.1/32 is already in use.

Answer

The candidate configuration has no errors and this is a warning.

Answer

The commit check command requires user confirmation.

Question 13

A network must forward traffic to 10.1.1.0/24 through a specific next-hop 192.168.1.1, even if a dynamic route with a lower preference is available. Which configuration will achieve this?

Accepted Answer

Configure a static route to 10.1.1.0/24 with next-hop 192.168.1.1 and preference 5.. A static route can be configured with a preference value lower than any dynamic routing protocol's default preference. In Junos, the default preference for OSPF internal routes is 10, for IS-IS level 1 is 15, for RIP is 100, and for BGP is 170. By setting the static route to 10.1.1.0/24 with next-hop 192.168.1.1 and preference 5, it will have a lower preference value than these defaults. Therefore, even if a dynamic route with a lower preference (i.e., a smaller number but still greater than 5) exists, the static route will be installed in the routing table and used for forwarding, satisfying the requirement to always forward traffic through the specified next-hop.

Answer

Configure the dynamic protocol to export the route with a metric of 1.

Answer

Configure a filter to reject the dynamic route.

Answer

Configure a static route to 10.1.1.0/24 with next-hop 192.168.1.1 and preference 15.

Question 14

A network engineer configures a static route to a remote network. They want the route to be automatically removed from the routing table if the directly connected interface used to reach the next hop fails. Which configuration approach should be used?

Accepted Answer

Configure the next-hop as the interface name.. Configuring the next-hop as an interface name (e.g., ge-0/0/0) creates a static route that is automatically removed from the routing table when that interface goes down. This is due to the route being 'qualified' by the interface's operational state; if the interface fails, the route is withdrawn. In contrast, using an IP address as the next-hop does not tie the route to the interface's state, so the route remains even if the interface fails, as long as the next-hop is reachable via another path.

Answer

Configure a higher metric on the static route.

Answer

Configure a preference of 0 on the static route.

Answer

Configure the next-hop as an IP address.

Question 15

Which command is used to verify that the current active configuration is the same as the candidate configuration?

Accepted Answer

show | compare. The command `show | compare` displays the differences between the candidate configuration and the active (committed) configuration. If there are no differences, the candidate configuration is identical to the active configuration. This is the correct way to verify whether the candidate configuration matches the active configuration in Junos.

Answer

commit check

Answer

show configuration

Answer

show system configuration

Question 16

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?

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 17

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 18

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 19

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 20

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