JN0-106 Junos Configuration Basics Practice Test 3 — 15 Questions

Question 1

Refer to the exhibit. What is the most likely cause of the commit check failure?

Accepted Answer

The 'family inet' statement is missing under unit 0.. In Junos, the 'disable' statement is used to administratively disable an interface. This is a valid configuration and does not cause a commit check failure. The commit check would succeed, and the interface would simply be operationally down. A common cause of commit check failure is referencing an interface in a routing instance without the required protocol family configured, such as missing 'family inet' under unit 0. This generates a commit error because the routing instance expects the interface to support the address family.

Answer

The routing instance has not been created.

Answer

The interface xe-0/0/0 has been disabled using the 'disable' statement.

Answer

The IP address is a duplicate on the subnet.

Question 2

Refer to the exhibit. An administrator wants to remove the address 10.0.0.2/24 from unit 0. Which configuration mode command achieves this without affecting other configuration?

Accepted Answer

delete interfaces ge-0/0/1 unit 0 family inet address 10.0.0.2/24. The command `delete interfaces ge-0/0/1 unit 0 family inet address 10.0.0.2/24` specifically removes only the IPv4 address 10.0.0.2/24 from the logical unit 0, leaving all other configuration (such as other addresses, VLAN tagging, or protocol families) intact. In Junos, addresses are hierarchical under `family inet address`, and deleting a specific address entry does not affect sibling addresses or the unit itself.

Answer

delete interfaces ge-0/0/1 unit 0

Answer

delete interfaces ge-0/0/1 unit 0 family inet address

Answer

delete interfaces ge-0/0/1 unit 1 family inet address 10.0.0.2/24

Question 3

An administrator is configuring a new Junos device and wants to ensure that configuration changes are applied only after explicit commit confirmation. Which configuration statement should be used?

Accepted Answer

commit confirmed. The 'commit confirmed' statement allows an administrator to apply configuration changes that automatically revert to the previous configuration if not explicitly confirmed within a specified timeout period (default 10 minutes). This ensures changes are only permanently applied after an explicit 'commit' confirmation, providing a safety mechanism to prevent lockout or misconfiguration.

Answer

commit synchronize

Answer

commit at

Answer

commit check

Question 4

A network engineer needs to configure an interface on a Juniper device to use DHCP to obtain an IP address. Which hierarchy is used to apply this configuration?

Accepted Answer

set interfaces ge-0/0/0 unit 0 family inet dhcp. On Juniper devices, DHCP client functionality for IPv4 is configured under the `family inet` hierarchy within a logical interface unit. The command `set interfaces ge-0/0/0 unit 0 family inet dhcp` enables the interface to obtain an IPv4 address via DHCP, which is the standard method for dynamic address assignment on Ethernet interfaces.

Answer

set interfaces ge-0/0/0 dhcp-client

Answer

set interfaces ge-0/0/0 unit 0 family inet6 dhcp

Answer

set interfaces ge-0/0/0 unit 0 family ppp dhcp

Question 5

An administrator is troubleshooting a configuration issue where a route filter is unexpectedly dropping traffic. The filter uses an 'exact' match type. Which statement correctly describes the behavior of the 'exact' match type in a prefix list?

Accepted Answer

The route must match the prefix and prefix length exactly.. The 'exact' match type in a Junos prefix list requires the route's prefix and prefix length to match the specified prefix and length identically. This is defined in the Junos routing policy framework, where 'exact' is used for precise route filtering, such as matching a specific network like 192.168.1.0/24 without allowing any subnets or supernets.

Answer

The route mask must be equal to or greater than the specified prefix length.

Answer

The prefix 0.0.0.0/0 is never matched by 'exact' filters.

Answer

The route mask must be greater than the specified prefix length.

Question 6

When configuring OSPF on a Juniper router, an engineer applies the 'area 0.0.0.0 interface ge-0/0/1.0 passive' command. What is the effect of this configuration?

Accepted Answer

The interface will not send OSPF hellos, but the connected network will still be advertised in OSPF.. The 'passive' configuration on an OSPF interface in Junos prevents the interface from sending OSPF Hello packets, which stops the formation of neighbor adjacencies. However, the interface's connected network prefix is still advertised as a stub network in OSPF Type 1 LSAs, ensuring reachability to that subnet without dynamic neighbor relationships.

Answer

The interface will not be advertised in OSPF at all, and no OSPF traffic will be transmitted.

Answer

The interface will only accept incoming OSPF packets but will not send any.

Answer

The interface will actively send OSPF hellos and attempt to form adjacencies.

Question 7

A network administrator is configuring a GRE tunnel on a Juniper device. The tunnel source is loopback 0 and destination is 192.0.2.1. Which additional configuration is necessary on the tunnel interface for the tunnel to become operational?

Accepted Answer

set interfaces gr-0/0/0 unit 0 family inet. A GRE tunnel interface on Junos requires the 'family inet' statement to be configured under the unit to enable IPv4 traffic forwarding. Without this, the tunnel interface will not have an IPv4 protocol family, and the device will not be able to route packets into or out of the tunnel, leaving it operationally down.

Answer

set interfaces gr-0/0/0 unit 0 mtu 1476

Answer

set interfaces gr-0/0/0 unit 0 multicast

Answer

set interfaces gr-0/0/0 unit 0 family inet6

Question 8

An administrator is configuring a static route to a remote network 10.10.10.0/24 via next-hop 192.168.1.1. Which command correctly adds this route?

Accepted Answer

set routing-options static route 10.10.10.0/24 next-hop 192.168.1.1. The Junos syntax for configuring a static route uses the hierarchy `set routing-options static route next-hop

`. The prefix must include the subnet mask in CIDR notation (e.g., /24). This command installs a route to 10.10.10.0/24 with next-hop 192.168.1.1 into the routing table.

Answer

set routing-options route 10.10.10.0/24 static next-hop 192.168.1.1

Answer

set routing-options static route 10.10.10.0 next-hop 192.168.1.1 mask 255.255.255.0

Answer

set routing-options static next-hop 192.168.1.1

Question 9

A junior engineer is tasked with configuring a firewall filter to only allow SSH access to the management interface. The management interface is fxp0. Which configuration is correct?

Accepted Answer

set interfaces fxp0 unit 0 family inet filter input allow-ssh. The management interface on Juniper devices is fxp0, and applying a firewall filter to its inet family input direction restricts inbound traffic. The filter 'allow-ssh' must permit only TCP port 22, blocking all other management access. This configuration ensures SSH-only access to the management interface.

Answer

set interfaces lo0 unit 0 family inet filter input allow-ssh

Answer

set groups management-filter interfaces fxp0 unit 0 family inet filter input allow-ssh

Answer

set interfaces ge-0/0/0 unit 0 family inet filter input allow-ssh

Question 10

While troubleshooting a routing loop, an administrator captures traffic on an interface and sees packets with TTL=1 being forwarded. This indicates a potential misconfiguration. Which command can be used to verify whether the interface is configured with 'no-ttl-propagate'?

Accepted Answer

show interfaces ge-0/0/0 detail. The 'no-ttl-propagate' configuration is applied at the interface level to prevent TTL decrement for certain protocols like MPLS. To verify this setting, you must check the interface configuration details, which are displayed by 'show interfaces ge-0/0/0 detail'. This command shows all interface properties, including any TTL propagation settings, whereas the configuration-only view may omit operational defaults.

Answer

show configuration interfaces ge-0/0/0

Answer

monitor traffic interface ge-0/0/0

Answer

show route forwarding-table

Question 11

Refer to the exhibit. The administrator applied a firewall filter named BLOCK-ICMP on the inbound direction of ge-0/0/0. However, pings from the router to 10.0.0.2 are successful. Why is this?

Accepted Answer

The filter is applied to transit traffic only; locally generated traffic bypasses the input filter.. In Junos, firewall filters applied to the input direction of an interface are evaluated for packets received on the interface, including packets destined to the router itself. However, packets that are locally generated by the router (such as an ICMP echo request) do not enter the interface; they are transmitted out through the interface. Therefore, the inbound BLOCK-ICMP filter on ge-0/0/0 does not apply to the ping traffic, so the ping succeeds. To filter locally generated traffic, you would use an output filter on the egress interface or a loopback filter.

Answer

The filter configuration is incorrect; the name should be within quotes.

Answer

The filter is applied to output traffic, not input traffic.

Answer

The BLOCK-ICMP filter allows ICMP by default.

Question 12

Refer to the exhibit. A route policy named DENY-RFC1918 is configured. What is the final action of this policy for a route matching 172.20.0.0/16?

Accepted Answer

The route is rejected because it matches the prefix list.. The route policy DENY-RFC1918 uses a prefix list that matches RFC 1918 private addresses, including 172.20.0.0/16 (which falls within the 172.16.0.0/12 range). Since the route matches the prefix list, term 1 applies a 'reject' action, and because no subsequent term explicitly accepts the route, the final action is reject.

Answer

The route is accepted because it does not match the prefix list.

Answer

The route is accepted because term 2 accepts all routes.

Answer

The route is rejected only if the prefix is exactly 172.16.0.0/12.

Question 13

Refer to the exhibit. The administrator has configured a default static route. However, the route does not appear in the routing table. Based on the output, what is the most likely issue?

Accepted Answer

The route is actually present and active in the routing table.. The exhibit shows the static route 0.0.0.0/0 with a next-hop of 10.0.0.1 in the routing table, indicated by the 'S' flag (static) and the active route marker '>'. The route is present and active, so the administrator's assumption that it does not appear is incorrect.

Answer

The static route is not configured correctly; the prefix is missing.

Answer

The route has been overwritten by a dynamic routing protocol.

Answer

The next-hop is unreachable because ge-0/0/0 is down.

Question 14

Which TWO statements about the 'commit' operation in Junos are correct?

Accepted Answer

The commit operation validates syntax before applying, and if errors are found, the commit fails.. The commit operation in Junos first validates the candidate configuration for syntax and semantic consistency. If errors are detected, the commit fails and the candidate configuration remains unchanged. Option E is correct because the commit operation activates the candidate configuration as the new active configuration, making it the running configuration. Options B, C, and D are incorrect: the 10-minute rollback timer is a feature of 'commit confirmed', not the standard commit; Junos does not support partial commits (the entire candidate configuration is always committed); and commit applies changes immediately, not at reboot.

Answer

The commit operation automatically rolls back changes after 10 minutes if not confirmed.

Answer

The commit operation allows you to commit only a specific portion of the configuration.

Answer

The commit operation applies the configuration changes at the next system reboot.

Question 15

Which THREE statements correctly describe the behavior of the 'replace pattern' command in Junos configuration mode?

Accepted Answer

It can be used to change interface names or IP addresses throughout the configuration.. The 'replace pattern' command in Junos configuration mode uses regular expressions to find and replace text strings across the entire candidate configuration, making it ideal for bulk changes such as renaming interfaces or updating IP addresses. This command operates on the candidate configuration (option D) and relies on regex patterns (option E), but it does not validate the replacement syntax (option A) nor automatically commit changes (option B).

Answer

It validates the replacement configuration for correctness before applying.

Answer

It automatically commits the changes after replacement.