JN0-106 Junos Configuration Basics — 15 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?

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

Accepted Answer

Define the filter under 'firewall family inet' and apply it under 'interfaces lo0 unit 0 family inet filter input filter-name'. To restrict SSH access to the device, the filter should be applied to the loopback interface (lo0) because all local control-plane traffic is received on lo0. Applying to a single physical interface (ge-0/0/0) only filters traffic on that interface and does not protect SSH access from other interfaces. The correct configuration is: 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 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

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. A, B, and D are all valid ways to change the hostname and commit. A and D use the full path 'set system host-name Core-Router; commit' from the top of configuration mode. B uses 'edit system' to enter the [edit system] hierarchy, then 'set host-name Core-Router; commit' — this is also valid because 'set host-name' is interpreted relative to [edit system] and commit commits the candidate configuration. Option C is invalid because the Junos statement is 'host-name', not 'hostname'.

Answer

set system hostname Core-Router; commit

Question 3

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. 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 4

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 5

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 candidate configuration is the configuration being edited but not yet committed. To view it, you must be in configuration mode and use the 'show' command. The 'show configuration' command is used in operational mode to display the active committed configuration. Therefore, none of the provided options is correct.

Answer

show configuration | display set

Answer

show configuration | compare rollback 0

Answer

show interface terse

Question 6

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. 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 7

After making several configuration changes, an engineer wants to see what changes were made in the candidate configuration compared to the last committed configuration. Which command should be used?

Accepted Answer

show configuration | compare. The 'show configuration | compare' command displays the differences between the candidate configuration and the active committed configuration. This pipe filter compares the current candidate configuration against the last committed configuration, showing added, changed, or deleted lines with '+' and '-' prefixes, which directly meets the engineer's requirement.

Answer

show configuration

Answer

show system rollback

Answer

show log messages

Question 8

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

Accepted Answer

Multiple users can make changes simultaneously in configure private mode.. 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 9

Which THREE are valid methods to apply a firewall filter in Junos?

Accepted Answer

Apply the filter to an interface under 'family inet filter input'. In Junos, a firewall filter is applied to an interface by configuring it under the 'family inet' hierarchy with the 'filter input' statement. This directs the filter to inspect all inbound IPv4 packets on that interface before they are processed by the routing engine.

Answer

Apply the filter globally using 'firewall family inet filter filter-name'

Answer

Apply the filter under 'routing-options'

Question 10

Which TWO are correct statements about the Junos configuration hierarchy?

Accepted Answer

The 'interfaces' hierarchy is used to configure physical and logical interfaces.. 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 11

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.. 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 12

Refer to the exhibit. An engineer notices that SNMP traffic from source 10.1.1.1 is being rejected on interface ge-0/0/1. The engineer wants to allow SNMP from this source while still blocking other SNMP traffic from the 10.0.0.0/8 range. Which change should be made?

Accepted Answer

Insert a term 0 before term 1 to permit SNMP from 10.1.1.1. Firewall filters in Junos are evaluated sequentially from the lowest term number. By inserting a new term 0 before the existing term 1 that explicitly permits SNMP traffic (UDP ports 161/162) from source 10.1.1.1, the filter will match and accept this traffic before reaching the deny term for the 10.0.0.0/8 range. This ensures the specific host is allowed while still blocking other SNMP traffic from the broader subnet.

Answer

Add a term at the end to permit all from 10.1.1.1

Answer

Change the source-address in term 1 to 10.0.0.0/8 except 10.1.1.1

Answer

Remove the filter and apply a new filter that permits SNMP from 10.1.1.1

Question 13

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 14

Refer to the exhibit. An engineer configures interface ge-0/0/0 with both IPv4 and IPv6 addresses. The engineer notices that the interface is operationally up, but the IPv6 address is not pingable from a directly connected host. The host has an IPv6 address in the same subnet. What is the most likely cause?

Accepted Answer

The interface does not have IPv6 neighbor discovery enabled.. On Junos, configuring an IPv6 address under family inet6 automatically enables Neighbor Discovery. It can only be disabled with 'no-neighbor-discovery'. Since the question does not indicate that this statement is present, the interface would have ND enabled, so B cannot be the most likely cause. No other option is a likely cause based on the information provided, so the question is invalid.

Answer

The interface MTU is too small for IPv6 packets.

Answer

The IPv6 address is not configured under the correct unit.

Answer

The interface has an IPv4 address, which prevents IPv6 from working.

Question 15

Your company has deployed a Juniper MX router at a branch office. The router has two upstream connections to different ISPs. The configuration currently uses a single static default route to ISP-A. The network team wants to add redundancy so that if ISP-A fails, traffic automatically uses ISP-B. The ISP-B connection is already configured on interface ge-1/0/0 with IP address 203.0.113.2/30. The next-hop IP for ISP-B is 203.0.113.1. The routing table should have a backup default route with a higher metric. Which configuration change meets the requirement?

Accepted Answer

set routing-options static route 0.0.0.0/0 next-hop 203.0.113.1 metric 2. It adds a static default route to ISP-B with a metric of 2, which is higher than the existing route's metric (default 0). In Junos, when multiple static routes to the same destination exist, the route with the lower metric is preferred and installed in the routing table. The higher-metric route serves as a backup and becomes active only if the primary route becomes unavailable (e.g., next-hop unreachable).

Answer

set routing-options static route 0.0.0.0/0 next-hop 203.0.113.1 metric 1

Answer

set routing-options static route 0.0.0.0/0 discard

Answer

set routing-options static route 0.0.0.0/0 next-table inet.0