JNCIA-JUNOS Practice Questions 2 — 50 Questions

Question 1

A network engineer is configuring a new Juniper device. They intend to apply a firewall filter to an interface to only allow SSH traffic from a specific management subnet. Which configuration approach best follows Juniper best practices?

Accepted Answer

Define the filter under 'firewall family inet' and apply it under 'interfaces ge-0/0/0 unit 0 family inet filter input filter-name'. Option A is correct because it follows Juniper best practices by defining the firewall filter under the `firewall family inet` hierarchy (which is the standard location for IPv4 filters) and applying it as an input filter on the physical interface `ge-0/0/0 unit 0 family inet`. This configuration ensures that only SSH traffic from the specified management subnet is permitted inbound on that interface, while all other traffic is dropped by default (since firewall filters in Junos have an implicit deny at the end).

Answer

Define the filter under 'firewall family inet' and apply it under 'interfaces lo0 unit 0 family inet filter input filter-name'

Answer

Define the filter under 'firewall family inet' and apply it under 'interfaces ge-0/0/0 unit 0 family inet input'

Answer

Define the filter under 'firewall family any' and apply it under 'interfaces ge-0/0/0 unit 0 family any filter input'

Question 2

An engineer is designing a network and needs to ensure that management traffic (SSH, SNMP) is always permitted, even if an interface firewall filter is applied. Which Juniper best practice should be followed?

Accepted Answer

Apply a firewall filter on the loopback interface (lo0) to protect the device. Applying a firewall filter to the loopback interface (lo0) is the Juniper best practice for protecting management traffic because the loopback interface is the logical termination point for all control plane traffic, including SSH and SNMP. This ensures that management traffic is always permitted regardless of which physical interface it arrives on, while still allowing interface-specific filters to be applied for data plane traffic without risk of blocking management access.

Answer

Use a firewall filter that permits all management traffic at the top of the list on each interface

Answer

Apply a firewall filter to the management interface (fxp0)

Answer

Disable the firewall filter on all interfaces

Question 3

Which TWO are correct statements about the Junos configuration hierarchy?

Accepted Answer

The 'interfaces' hierarchy is used to configure physical and logical interfaces.. Option B is correct because the 'interfaces' hierarchy in Junos is specifically designed to configure both physical interfaces (e.g., ge-0/0/0) and logical interfaces (e.g., ge-0/0/0.100), including parameters like IP addresses, MTU, and VLAN tagging. This is a fundamental part of Junos configuration, as all network traffic flows through interfaces defined under this hierarchy.

Answer

The 'routing-options' hierarchy is used to configure interface IP addresses.

Answer

Firewall filters are configured under 'policy-options'.

Answer

The 'protocols' hierarchy includes system-level settings like hostname.

Question 4

A junior engineer is asked to change the hostname of a Juniper device from 'Router-1' to 'Core-Router'. Which command sequence correctly commits the change?

Accepted Answer

set system host-name Core-Router; commit. Option A is correct because the Junos CLI uses the 'set system host-name' command (with a hyphen in 'host-name') to change the device hostname, and 'commit' applies the change to the active configuration. The command sequence is syntactically valid and follows Junos configuration hierarchy.

Answer

edit system; set host-name Core-Router; commit

Answer

set system hostname Core-Router; commit

Answer

set system host-name Core-Router; commit

Question 5

A network engineer needs to add an additional IP address to an interface that already has a primary IP configured. Which method should be used?

Accepted Answer

set interfaces ge-0/0/0 unit 0 family inet address 10.0.0.2/24 secondary. Option B is correct because in Junos, to add an additional IP address to an interface that already has a primary IP configured, you must append the 'secondary' keyword to the address configuration statement. This allows multiple IPv4 addresses on the same logical interface unit, with the first address assigned being the primary and subsequent addresses marked as secondary.

Answer

set interfaces ge-0/0/0 unit 0 family inet address 10.0.0.2/24

Answer

set interfaces ge-0/0/0 unit 0 family inet secondary address 10.0.0.2/24

Answer

set interfaces ge-0/0/0 unit 0 family inet address 10.0.0.2/24 primary

Question 6

A network engineer wants to schedule a reboot of a Juniper device at 3:00 AM. Which command should be used?

Accepted Answer

request system reboot at 03:00. Option C is correct because the 'request system reboot at 03:00' command schedules a one-time reboot of the Juniper device at the specified time (3:00 AM). The 'at' parameter allows the engineer to set an absolute time for the reboot, which is the exact requirement for scheduling a reboot at a specific future time.

Answer

request system configuration rescue save

Answer

request system reboot

Answer

load override /config/juniper.conf.gz

Question 7

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 8

During troubleshooting, an engineer notices that BGP sessions are flapping. They suspect that the issue might be related to the maximum number of routes allowed. To see if the BGP import policy is rejecting routes, which operational command would provide immediate insight?

Accepted Answer

show bgp neighbor x.x.x.x. Option D is correct because the 'show bgp neighbor x.x.x.x' command displays detailed BGP session information, including the number of received and accepted routes, as well as any prefix-limit or policy-related rejections. If the BGP import policy is rejecting routes due to exceeding the maximum allowed, this command will show the 'received prefixes' count alongside the 'accepted prefixes' count, immediately revealing if routes are being dropped. This provides direct insight into whether the flapping is caused by route limit enforcement.

Answer

show version

Answer

show interfaces terse

Answer

show route protocol bgp

Question 9

Refer to the exhibit. An engineer has made changes to the candidate configuration. What will happen when the engineer issues the 'commit' command?

Accepted Answer

Both the interface address and security policy will be activated.. Option D is correct because in Junos, the 'commit' command activates all changes in the candidate configuration atomically. Both the interface address change and the security policy will be applied simultaneously after validation. Junos does not require a reboot for security policy changes, and syntax errors cause the commit to fail, not be ignored.

Answer

The commit will succeed but the security policy will be ignored due to a syntax error.

Answer

Only the interface address change will be committed because security policies require a reboot.

Answer

The configuration will be validated; if errors exist, the commit will fail.

Question 10

Refer to the exhibit. An engineer wants to verify that static routes for 10.0.1.0/24 and 10.0.2.0/24 are present in the routing table. Based on the output, which statement is true?

Accepted Answer

Both routes are active and have the same preference value.. The output shows both 10.0.1.0/24 and 10.0.2.0/24 as static routes with a preference of 5. Since the preference value is the same and both are listed as active (the 'A' flag is present in the routing table), both routes are installed and active in the forwarding table. In Junos, a static route's default preference is 5, and any route with a lower preference is preferred; here both have equal preference, so they coexist as active routes.

Answer

Both routes have a preference of 0.

Answer

Only the 10.0.1.0/24 route is active.

Answer

Both routes use the same next-hop IP address.

Question 11

Refer to the exhibit. How many static default routes are configured?

Accepted Answer

2. Option D is correct because the exhibit shows two static routes with a next-hop of 0.0.0.0, which are static default routes. In JUNOS, a static default route is defined by a destination prefix of 0.0.0.0/0 (or ::/0 for IPv6). The configuration lists two such routes, each with a different next-hop address, confirming two static default routes.

Answer

1

Answer

0

Answer

3

Question 12

An organization has two ISPs and wants to load-balance traffic equally across both links for all outbound traffic. Which routing configuration approach should be used?

Accepted Answer

Configure two static default routes with equal metric values and enable ECMP.. Option C is correct because configuring two static default routes with equal metric values and enabling Equal-Cost Multi-Path (ECMP) allows the Juniper device to load-balance outbound traffic equally across both ISP links. ECMP uses per-flow or per-packet load balancing based on the hash of source/destination IP addresses and ports, ensuring traffic is distributed evenly without relying on dynamic routing protocols.

Answer

Configure two static default routes with different metric values.

Answer

Configure policy-based routing to match all traffic and forward to both ISPs.

Answer

Establish BGP sessions with both ISPs and rely on BGP path selection.

Question 13

When configuring a new Juniper router, an engineer needs to ensure that configuration changes are not automatically committed after a certain time if not explicitly confirmed. Which configuration parameter controls this?

Accepted Answer

commit confirmed. The 'commit confirmed' command is used to apply a configuration change that will automatically roll back to the previous configuration if not explicitly confirmed within a specified time period (default 10 minutes). This ensures that changes are not permanently applied unless the engineer verifies them, preventing accidental lockout or misconfiguration.

Answer

commit check

Answer

commit at

Answer

commit synchronize

Question 14

Which TWO statements are true regarding the Junos OS commit model?

Accepted Answer

Multiple users can make changes simultaneously in configure private mode.. Option C is correct because Junos OS allows multiple users to enter configure private mode, where each user has an independent candidate configuration. This prevents conflicts and allows simultaneous edits without interfering with each other's changes. Option E is correct because the 'commit' command activates the candidate configuration, making it the active configuration on the device.

Answer

Configuration changes are activated immediately upon entering the 'set' command.

Answer

The 'commit check' command activates the candidate configuration if syntax is valid.

Answer

The 'commit confirmed' command automatically commits changes permanently.

Question 15

During a routing table lookup, a packet matches both a static route and an OSPF route to the same destination. Which route will be installed in the forwarding table?

Accepted Answer

The static route, because it has a lower preference value.. In Junos, the route with the lowest preference value is installed in the forwarding table. Static routes have a default preference of 5, while OSPF internal routes have a default preference of 10. Therefore, the static route is preferred and installed.

Answer

Both routes, if they are equal-cost.

Answer

The route with the higher preference value.

Answer

The OSPF route, because OSPF is a dynamic routing protocol.

Question 16

Refer to the exhibit. Which route is active for the 192.168.1.0/24 prefix?

Accepted Answer

The OSPF route because it is marked with an asterisk.. In JUNOS, the active route for a prefix is determined by the route preference (administrative distance). OSPF has a default preference of 10, while a static route has a default preference of 5. However, the exhibit shows the OSPF route with an asterisk (*), which in JUNOS indicates the active route in the routing table. Since the OSPF route is marked with an asterisk, it is the active route, and the static route is a backup. Option D is correct because the asterisk signifies the active route, and OSPF's preference is higher (less preferred) than the static route's preference, but the asterisk overrides that assumption in this context.

Answer

Both routes are active.

Answer

The static route because it has a lower preference.

Answer

Neither route is active.

Question 17

A network administrator wants to filter routes from being installed in the routing table based on certain criteria. Which Junos feature should be used?

Accepted Answer

Routing policy (import). B is correct because a routing policy with an import term is the Junos mechanism to control which routes are accepted into the routing table from a routing protocol or a peer. By defining match conditions (e.g., prefix, community, AS path) and an action (accept or reject), the administrator can filter routes before they are installed. This is the standard Junos approach for route filtering at the routing table level.

Answer

Community list

Answer

Prefix list

Answer

Firewall filter

Question 18

A network administrator wants to view the current candidate configuration that has not yet been committed. Which command should be used?

Accepted Answer

show configuration. The command 'show configuration' displays the current candidate configuration that has been staged but not yet committed. In Junos, the candidate configuration is stored separately from the active (committed) configuration, and this command shows all uncommitted changes. Option B is correct because it directly retrieves the candidate configuration without any comparison or filtering.

Answer

show configuration | display set

Answer

show configuration | compare rollback 0

Answer

show interface terse

Question 19

A network engineer is configuring a new Juniper device and needs to ensure that the configuration is saved persistently across reboots. Which command should be used?

Accepted Answer

commit. The `commit` command activates the candidate configuration and saves it to the active configuration database, ensuring it persists across reboots. Without a commit, any changes made in candidate mode are lost when the device restarts.

Answer

save

Answer

request system reboot

Answer

show configuration

Question 20

Which TWO statements correctly describe the function of the 'commit' command in Junos OS? (Choose two.)

Accepted Answer

It validates the candidate configuration for syntax errors.. Option A is correct because the 'commit' command in Junos OS first validates the candidate configuration for syntax errors before applying it. If syntax errors are found, the commit fails and the candidate configuration is not applied, ensuring the device does not enter an inconsistent state. This validation step is a core part of Junos's transactional configuration model, where changes are staged in a candidate configuration and then committed atomically.

Answer

It schedules the configuration to be applied at a later time.

Answer

It discards the candidate configuration after saving.

Answer

It automatically reboots the device to apply the changes.