JN0-106 Practice Test 3 — 30 Questions

Question 1

An administrator notices that after committing a configuration change on a Juniper MX router, the device loses connectivity to the management network. The management interface is part of a dedicated management routing instance. Which of the following is the most likely cause?

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

Accepted Answer

The routing instance for the management interface was accidentally removed. The management interface is part of a dedicated management routing instance (often named mgmt_junos). If this routing instance is accidentally removed during a commit, the management interface loses its routing context and becomes unreachable, causing loss of connectivity to the management network. This is a common misconfiguration when an administrator modifies routing instance configurations without realizing the management interface depends on it.

Answer

A firewall filter was applied to the management interface that blocks all traffic

Answer

NTP was configured with an incorrect server address

Answer

A syslog server was configured that is unreachable

Question 2

Refer to the exhibit. Why is the route for 192.168.1.0/24 hidden?

Accepted Answer

The next-hop is unreachable. A route is hidden in the JUNOS routing table when its next-hop is unreachable. The show route command displays only active routes; if the next-hop address is not reachable via any active interface or route, the route is suppressed (hidden) and not used for forwarding. This is a fundamental behavior of JUNOS route selection and differs from Cisco IOS, which may still display such routes.

Answer

The route has a higher metric

Answer

The route has a lower preference

Answer

The route is not committed

Question 3

Which two events typically trigger a change to the routing table? (Choose two.)

Accepted Answer

Interface state change. An interface state change (up/down) directly affects the reachability of directly connected networks. When an interface goes up, Junos adds the corresponding directly connected route to the routing table; when it goes down, the route is removed. Similarly, a BGP neighbor reset causes the BGP session to be torn down and re-established, which triggers the withdrawal and re-advertisement of all BGP routes, thereby modifying the routing table.

Answer

System uptime

Answer

Log file rotation

Answer

Configuration commit

Question 4

Which Junos CLI mode allows a user to view the configuration and execute operational commands, but not make configuration changes?

Accepted Answer

Operational mode. In Junos OS, Operational mode (indicated by the `>` prompt) allows users to execute operational commands (e.g., `show`, `ping`, `traceroute`) and view the active configuration using `show configuration`, but it does not permit any changes to the configuration. Configuration changes require entering Configuration mode (indicated by the `#` prompt) via the `configure` command. This separation enforces a strict two-tier access model, ensuring that operational tasks do not inadvertently alter the device's configuration.

Answer

Monitor mode

Answer

Enable mode

Answer

Configuration mode

Question 5

You are a network engineer responsible for a Juniper MX240 router in a data center. The router is running Junos 18.2R1 and you need to upgrade it to 19.1R2 to fix a critical security vulnerability. You establish an SSH session to the router and enter configuration mode to prepare the upgrade. While in configuration mode, you notice that the candidate configuration contains several uncommitted changes from a previous engineer that attempted to modify BGP settings but introduced a syntax error. The candidate configuration fails any commit operation due to this error. The currently active configuration is stable and the router is handling production traffic. The upgrade process requires you to change the boot media and specify the new image. Which action should you take to clear the candidate configuration and proceed with the upgrade?

Accepted Answer

Execute the 'rollback 0' command to discard the candidate and replace it with the active configuration, then proceed with the upgrade commands.. The 'rollback 0' command discards all uncommitted changes in the candidate configuration and replaces it with the active, committed configuration. This clears the syntax error without affecting the running router, allowing you to proceed with the upgrade commands (e.g., 'request system software add') without a reboot or forced commit.

Answer

Reboot the router to clear the candidate configuration and then start the upgrade.

Answer

Run the 'load override terminal' command and paste the active configuration from memory, then commit and upgrade.

Answer

Use the 'commit force' command to override the syntax error and commit the candidate, then perform the upgrade.

Question 6

Based on the exhibit, what is the most likely impact on the router?

Accepted Answer

Routing protocol adjacencies will be lost, causing routing instability.. The exhibit shows kernel messages indicating a hardware or software fault (e.g., a FPC crash or PIC restart). In Junos, such critical events cause the Packet Forwarding Engine (PFE) to reset, which tears down all routing protocol adjacencies (OSPF, BGP, IS-IS) because the control plane loses communication with the forwarding plane. This leads to route withdrawal and routing instability until the adjacencies are re-established.

Answer

The CPU will be overloaded due to the kernel messages.

Answer

The router will stop forwarding packets immediately.

Answer

The router will reboot automatically.

Question 7

A network administrator is troubleshooting a missing route in the routing table. The route is learned via OSPF, and the OSPF neighbor adjacency is up. Which command would help determine if OSPF received the route?

Accepted Answer

show ospf database. The OSPF link-state database (LSDB) contains all received LSAs, including Type 1 (Router) and Type 3 (Summary) LSAs that advertise routes. Even if a route is not installed in the routing table (e.g., due to a higher administrative distance or a missing route preference), the 'show ospf database' command confirms whether OSPF has received the LSA carrying that route. This directly answers the question of whether OSPF received the route, independent of route installation.

Answer

show route protocol ospf

Answer

show ospf neighbor

Answer

show interface terse

Question 8

Refer to the exhibit. What does this command accomplish?

Accepted Answer

Displays syslog messages containing the word 'error'.. The command shown filters the output of the system log file to display only lines containing the substring 'error'. This allows the administrator to quickly see log entries related to errors, rather than viewing all messages or a dedicated error log file.

Answer

Displays help for syslog messages that include 'error'.

Answer

Displays all syslog messages.

Answer

Displays the error log file.

Question 9

Arrange the steps to configure an IPsec VPN on a Junos SRX in the correct order.

Accepted Answer

Step 1: Configure IKE proposals and policies (Phase 1). Step 2: Configure IPsec proposals and policies (Phase 2). Step 3: Configure security policies to permit VPN traffic. Step 4: Apply the IPsec VPN configuration to an interface (e.g., st0).. IPsec VPN setup involves IKE for key exchange, IPsec for encryption, and binding to an interface.

Answer

Step 1: Configure IPsec proposals and policies (Phase 2). Step 2: Configure IKE proposals and policies (Phase 1). Step 3: Apply the IPsec VPN configuration to an interface. Step 4: Configure security policies.

Answer

Step 1: Configure security policies to permit VPN traffic. Step 2: Configure IKE proposals and policies. Step 3: Configure IPsec proposals and policies. Step 4: Apply the IPsec VPN configuration to an interface.

Answer

Step 1: Apply the IPsec VPN configuration to an interface. Step 2: Configure IKE proposals and policies. Step 3: Configure IPsec proposals and policies. Step 4: Configure security policies.

Question 10

An engineer wants to configure a static route that will be used only if the primary route (learned via OSPF) becomes unavailable. Which feature should be used?

Accepted Answer

Floating static route with a higher preference.. A floating static route is configured with a higher preference (administrative distance) than the OSPF-learned route. Since JUNOS prefers routes with lower preference values, the static route will only be installed in the routing table when the OSPF route is withdrawn, providing a backup path.

Answer

Static route with a lower metric.

Answer

Reverse path forwarding.

Answer

Routing policy.

Question 11

Refer to the exhibit. An engineer runs the command shown. What does this output indicate?

Accepted Answer

The candidate configuration has an IP address change.. The output shows the candidate configuration differs from the committed configuration, as indicated by the 'show | compare' command displaying a change under the [edit interfaces ge-0/0/0 unit 0 family inet] hierarchy. Specifically, it shows the address 192.168.1.1/24 being replaced with 192.168.1.2/24, which is an IP address change. This confirms option B is correct because the candidate configuration has an IP address change that has not yet been committed.

Answer

The candidate configuration matches the committed configuration.

Answer

The rollback 0 configuration is being displayed.

Answer

The interface ge-0/0/0 has been deleted.

Question 12

Refer to the exhibit. An operator tries to ping 192.168.1.2 from this router and fails. The router can ping itself (192.168.1.1). What is the most likely cause?

Accepted Answer

The remote host is not reachable or is not responding to ARP requests.. The router can ping its own interface (192.168.1.1), confirming that the interface is up and IP is configured correctly. The failure to ping 192.168.1.2 indicates that the router cannot reach the remote host, most likely because the host is down, not connected, or not responding to ARP requests. ARP resolution is required for the router to map the destination IP to a MAC address on the local subnet; without a successful ARP reply, the router cannot send the echo request.

Answer

Reverse path forwarding (RPF) check is dropping the echo request.

Answer

The interface is administratively down.

Answer

Proxy ARP is not configured on the interface.

Question 13

You are a network engineer for a service provider that recently deployed a Juniper MX router at a new Point of Presence (PoP). The router is used to aggregate customer connections and exchange routes with upstream providers via BGP. After the initial configuration, you notice that the router is not learning any routes from one of the upstream BGP peers. You have verified that the BGP session is established (state Established) and that the peer is sending routes. You suspect that the issue might be related to the firewall filter or routing policy. You want to determine if any inbound routes are being rejected and why. Which command would provide the most direct information about why routes are being rejected?

Accepted Answer

show route receive-protocol bgp 192.0.2.1. 'show route receive-protocol bgp 192.0.2.1', is correct because it displays the exact routes received from a specific BGP peer along with any policy or filter actions applied (e.g., reject, accept). This command directly shows whether routes are being rejected and the reason (e.g., due to an import policy or firewall filter), making it the most direct diagnostic tool for the described issue.

Answer

show route protocol bgp

Answer

show bgp summary

Answer

show firewall filter <filter-name>

Question 14

Refer to the exhibit. The OSPF neighbor adjacency repeatedly goes up and down on R1. What is a likely cause?

Accepted Answer

MTU mismatch between the two routers. An MTU mismatch between OSPF neighbors can cause the adjacency to flap because OSPF includes the interface MTU in the Database Description (DBD) packets. If the MTU values do not match, the receiving router will reject the DBD packet, preventing the exchange of LSAs and causing the neighbor state to reset. This is a common cause of repeated up/down OSPF adjacencies even when the physical link is stable.

Answer

The physical link is flapping

Answer

OSPF authentication is misconfigured

Answer

The routers are in different OSPF areas

Question 15

Which configuration group feature allows an administrator to apply common configuration settings to multiple interfaces without repeating the configuration?

Accepted Answer

apply-groups. The `apply-groups` statement is the correct feature because it allows an administrator to define a common configuration template within a `groups` hierarchy and then apply that template to multiple interfaces (or other configuration sections) using the `apply-groups` command. This avoids repeating the same configuration statements across individual interfaces, streamlining management and reducing errors.

Answer

groups statement

Answer

interface-range

Answer

apply-path

Question 16

You are administering a Juniper MX240 router that provides connectivity to multiple customer sites. The router uses BGP to exchange routes with two upstream ISPs. Recently, you applied a new firewall filter to the loopback interface to restrict management access. After committing the configuration, you can no longer establish SSH sessions to the router from the management network. You are currently connected via console. The loopback filter is still applied. You suspect the filter is blocking SSH traffic from the management network. What should you do to restore SSH access without losing the other filter rules?

Accepted Answer

Add a new term at the beginning of the filter that accepts SSH traffic from the management network, then reorder the terms so that this term is evaluated first.. Firewall filters in Junos are evaluated in order, and adding a term at the beginning that explicitly accepts SSH traffic from the management network ensures that the SSH packets are permitted before any subsequent deny terms are evaluated. This preserves all existing filter rules while restoring SSH access. The 'insert' command or reordering terms is necessary to place the new term first, as the default behavior appends new terms to the end of the filter.

Answer

Roll back to the previous configuration using 'rollback 0' and commit.

Answer

Add a new term at the end of the filter that accepts SSH traffic from any source.

Answer

Delete the firewall filter from the loopback interface and commit.

Question 17

Order the steps to reset the root password on a Junos device via the console.

Accepted Answer

Power cycle the device, interrupt the boot process by pressing the space bar when prompted, select the recovery option (option 2) from the boot menu, set the new root password and reboot.. Root password recovery requires boot interruption and selecting the recovery option from the boot menu.

Answer

Power cycle the device, press Ctrl+C during Junos kernel load to enter the boot loader, type 'boot -s' at the loader prompt, then set the new root password and reboot.

Answer

Connect via SSH, run 'request system root-authentication plain-text-password', enter the new password, then reboot the device.

Answer

Boot the device normally, log in with any credentials, use 'cli' to enter CLI mode, run 'set system root-authentication plain-text-password', then reboot.

Question 18

Two routers running IBGP with full mesh have a routing loop for prefix 10.1.1.0/24. Both routers have an IBGP route (preference 170) for the prefix with next-hop 10.2.2.2, and an OSPF route (preference 10) for the same prefix. The OSPF next-hop on each router points to the other router's loopback interface. Which action should be taken to stop the loop while preserving BGP route advertisement?

Accepted Answer

Increase the OSPF preference for 10.1.1.0/24 to 175. Increasing the OSPF preference for 10.1.1.0/24 to 175 makes the IBGP route (preference 170) more preferred than the OSPF route. This breaks the routing loop where each router's OSPF route points to the other's loopback, while preserving the IBGP route advertisement. The loop occurs because both routers prefer the OSPF route (preference 10) over IBGP (preference 170), causing traffic to bounce between them.

Answer

Add a static route for 10.1.1.0/24 with next-hop 10.2.2.2

Answer

Configure 'set protocol bgp group internal-mesh local-address 10.2.2.2' to set next-hop to self

Answer

Use route reflection to break the loop

Question 19

An engineer configures a static route to 192.168.0.0/16 with next-hop 172.16.1.1. The static route appears as 'hidden' in the routing table. What is the most likely cause?

Accepted Answer

The next-hop address 172.16.1.1 is unreachable. In JUNOS, a static route with a next-hop that is not reachable (i.e., there is no active route to the next-hop) is automatically placed in a 'hidden' state. The most likely cause is that the next-hop 172.16.1.1 is unreachable.

Answer

The static route preference is set too high

Answer

The static route has not been committed

Answer

The static route is a discard route

Question 20

A senior network administrator is logged into a Juniper device in operational mode. They need to make a configuration change to the BGP group 'INTERNAL'. They type 'configure terminal' and receive 'unknown command'. They then type 'configure' and enter configuration mode. They make the needed changes and exit configuration mode using 'exit'. They then try to view the active configuration to verify the changes by typing 'show configuration | match INTERNAL'. They see no output. What is the most likely reason?

Accepted Answer

They should have used 'commit' before exiting configuration mode.. In Junos, configuration changes made in configuration mode are stored in a candidate configuration until explicitly committed using the 'commit' command. Exiting configuration mode with 'exit' does not discard the candidate configuration; the changes remain in the candidate but are not part of the active configuration. The 'show configuration' command displays the active (committed) configuration, which explains why no output matching 'INTERNAL' was seen. The administrator needed to use 'commit' to activate the changes before viewing them with 'show configuration'.

Answer

The command 'show configuration' only shows the candidate configuration, not the active.

Answer

They exited configuration mode without committing, so the changes were lost.

Answer

They need to be in configuration mode to run 'show configuration'.