JNCIA-JUNOS Timed Practice Test 4 — 10 Questions

Question 1

A network administrator is configuring a new interface and wants to ensure that the interface is enabled and can pass traffic. Which configuration element is required?

Accepted Answer

set interfaces ge-0/0/0 unit 0 family inet address 192.168.1.1/24. Option B is correct because in Junos, an interface is administratively enabled by default (no explicit 'enable' command is needed), but to pass traffic it requires a logical unit with a configured protocol family and an IP address. The command 'set interfaces ge-0/0/0 unit 0 family inet address 192.168.1.1/24' creates unit 0, assigns the IPv4 address, and implicitly enables the interface for traffic forwarding. Without an address under a family, the interface cannot pass IP traffic even if it is administratively up.

Answer

set interfaces ge-0/0/0 enable

Answer

set interfaces ge-0/0/0 unit 0 family inet

Answer

set interfaces ge-0/0/0 disable

Question 2

During a maintenance window, an engineer needs to apply a series of configuration changes that are stored in a text file. Which command sequence should be used to load and apply the changes from the file?

Accepted Answer

configure; load merge /var/tmp/changes.txt; commit. Option D is correct because the engineer needs to enter configuration mode (configure) and then use the 'load merge' command to merge the contents of the text file into the candidate configuration without replacing the entire configuration. The 'commit' command then activates the changes. This is the standard Junos workflow for applying incremental changes from a file.

Answer

request system configuration rescue save

Answer

load override /var/tmp/changes.txt; commit

Answer

configure; load patch /var/tmp/changes.txt; commit

Question 3

An engineer notices that a Juniper device is not saving configuration changes across reboots. What is the most likely cause?

Accepted Answer

The candidate configuration was not committed.. In Junos OS, configuration changes are stored in a candidate configuration and only become active and persistent across reboots after a 'commit' operation. Without a commit, the changes remain in the candidate buffer and are discarded upon reboot, causing the device to revert to the last committed configuration.

Answer

The rescue configuration is not set.

Answer

The device is booting from factory-default configuration.

Answer

The command 'request system reboot' was used instead of 'commit'.

Question 4

Which TWO statements are true about the Junos OS candidate configuration model? (Choose two.)

Accepted Answer

The candidate configuration can be modified without affecting the active configuration.. Option D is correct because the Junos OS candidate configuration model allows modifications to be made to a separate candidate configuration file without affecting the active configuration currently running on the device. This ensures that changes can be staged, reviewed, and validated before being committed, providing a safe and non-disruptive way to manage configuration changes.

Answer

Each change is applied incrementally to the active configuration.

Answer

The candidate configuration is stored in a separate file from the active configuration.

Answer

After a commit, the candidate configuration is automatically discarded.

Question 5

An engineer needs to apply a configuration change that adds a new static route to the Junos device. The engineer wants to ensure the change takes effect immediately and is persistent across reboots. Which command should the engineer use?

Accepted Answer

commit. The 'commit' command is correct because it immediately activates the candidate configuration (including the new static route) and makes it the active configuration that survives a reboot. Junos uses a two-stage configuration model where changes are first made to the candidate configuration and then committed to become the active, persistent configuration.

Answer

load override

Answer

commit confirmed

Answer

rollback

Question 6

A network engineer needs to view the operational status of all interfaces on a Junos device, including those that are disabled. Which command should be used?

Accepted Answer

show interfaces terse. The 'show interfaces terse' command displays a concise, one-line-per-interface summary of all interfaces, including their administrative status (up/down) and whether they are disabled. Unlike 'show interfaces', which by default only shows interfaces that are physically present and enabled, 'terse' includes interfaces that are administratively disabled (e.g., 'down' in the Admin column). This makes it the correct choice for viewing the operational status of all interfaces, including disabled ones.

Answer

show interfaces

Answer

show configuration interfaces

Answer

monitor interface traffic

Question 7

A network administrator notices that traffic between two VLANs is not reaching its destination. The switch has an IRB interface configured with an IP address in each VLAN's subnet. What is the most likely missing configuration?

Accepted Answer

The VLANs are not defined on the switch.. The IRB interface provides Layer 3 routing between VLANs, but it requires the VLANs themselves to be defined on the switch. If the VLANs are not defined, the switch cannot associate the IRB interface with the correct broadcast domains, and traffic will not be forwarded between them. Option C correctly identifies this missing configuration.

Answer

The IRB interface does not have an IP address configured.

Answer

The VLANs are on different switches.

Answer

The switch ports are not configured for VLAN tagging.

Question 8

Which TWO statements about Juniper's implementation of static routes are correct? (Choose two.)

Accepted Answer

The default preference for static routes is 5.. Option A is correct because in Juniper's Junos OS, the default preference (administrative distance) for static routes is 5. This value indicates that static routes are highly trusted, only surpassed by directly connected routes (preference 0). This is a Juniper-specific default, differing from Cisco's default of 1 for static routes.

Answer

Static routes always have a metric of 1.

Answer

Static routes are automatically redistributed into OSPF.

Answer

The default preference for static routes is 170.

Question 9

A network engineer is troubleshooting OSPF adjacencies between two Juniper routers. The routers are directly connected and have matching OSPF configurations except for the router IDs. Router A has router-id 10.0.0.1, Router B has router-id 10.0.0.2. The adjacency remains in the EXSTART state. What is the most likely cause?

Accepted Answer

The MTU on the interface is mismatched.. The EXSTART state indicates that the routers have progressed past the 2-Way state and are attempting to exchange Database Description (DBD) packets. A common cause for getting stuck in EXSTART is an MTU mismatch, because OSPF uses the interface MTU to determine the maximum size of DBD packets. If Router A's MTU is larger than Router B's, Router B will drop the oversized DBD packet and the adjacency will remain in EXSTART.

Answer

The router IDs are not the same.

Answer

The area ID is not configured.

Answer

The hello and dead intervals are mismatched.

Question 10

Which THREE of the following statements are true regarding Junos OS commit operations?

Accepted Answer

The 'commit check' command validates the candidate configuration without activating it.. Option A is correct because the 'commit check' command validates the candidate configuration for syntax and semantic errors without activating it. This allows an administrator to verify changes before making them active, preventing potential misconfigurations from disrupting network operations.

Answer

You can run multiple commit scripts during a single commit operation.

Answer

The rollback command reverts to the current active configuration.