JN0-106 Practice Test 10 — 10 Questions

Question 1

Your company runs a Juniper MX480 router as the core gateway. The router has been experiencing intermittent connectivity issues with a remote site over a point-to-point OC3 link. Users report that the link goes down for a few seconds several times a day. You suspect that the issue might be related to physical layer errors or framing. You need to determine the cause and collect relevant data to present to the service provider. Which course of action should you take first?

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

Accepted Answer

Run 'monitor interface so-0/0/0' and observe for any CRC errors or alarms over a period of time.. 'monitor interface so-0/0/0' provides real-time, continuous display of interface counters and alarms, allowing you to observe CRC errors, framing errors, or alarms (e.g., LOS, LOF) as they occur. This is the most direct way to capture transient physical-layer issues on a SONET/SDH OC3 link without disrupting service, making it the appropriate first step before escalating to the service provider.

Answer

Perform a loopback test on the interface using 'test interface so-0/0/0'.

Answer

Review the system syslog file using 'show log messages' and search for interface down messages.

Answer

Immediately replace the serial interface card to rule out hardware failure.

Question 2

A network administrator makes several changes to the configuration but decides to discard all uncommitted changes and start fresh. Which command should be used to revert the candidate configuration back to the current active configuration?

Accepted Answer

rollback 0. The 'rollback 0' command reverts the candidate configuration to the currently active configuration, discarding all uncommitted changes. This is because Junos maintains a rollback database of the last 50 committed configurations, with index 0 always representing the active configuration. Using 'rollback 0' effectively resets the candidate configuration to match the active one, allowing the administrator to start fresh without affecting the running system.

Answer

load override

Answer

commit check

Answer

rollback 1

Question 3

A company is deploying an EVPN-VXLAN fabric with Juniper QFX switches. To provide inter-subnet routing, which interface type must be configured?

Accepted Answer

IRB interface. In an EVPN-VXLAN fabric, Integrated Routing and Bridging (IRB) interfaces are required to provide inter-subnet routing. IRB interfaces act as Layer 3 gateways within the VXLAN overlay, enabling routing between different VLANs/VXLANs by terminating both the bridge domain and the routing instance. Without IRB, traffic cannot be routed between subnets in the EVPN-VXLAN fabric.

Answer

Physical interface with vlan-tagging

Answer

VXLAN tunnel endpoint (VTEP)

Answer

Loopback interface

Question 4

A network operations team has received a new Juniper router to replace an existing legacy router. The team needs to apply a baseline configuration that includes system settings, interfaces, and security policies. The configuration is provided as a text file containing Junos configuration hierarchy syntax (e.g., 'system { host-name... }'). The engineer connects to the console and sees the prompt 'root@%'. What is the most efficient way to apply the configuration?

Accepted Answer

Use the 'load merge' command to merge the configuration file.. The engineer is at the shell prompt (root@%), not in configuration mode. The 'load merge' command is used within configuration mode to merge a configuration file (in Junos hierarchy syntax) into the candidate configuration, which is the most efficient way to apply a pre-written baseline configuration without manual typing or complex file transfers.

Answer

Use the 'load set' command to load a set of configuration commands.

Answer

Use FTP to transfer the file and then commit.

Answer

Enter configuration mode and manually type each command.

Question 5

An engineer needs to view the current active configuration of a Junos device without making any changes. Which CLI mode should they use?

Accepted Answer

Operational mode. Operational mode is the default CLI mode in Junos, used for monitoring, troubleshooting, and viewing the current active configuration without making any changes. Commands in this mode are read-only and do not modify the device's configuration. The active configuration is the one currently running on the device, and it can be viewed using commands like 'show configuration' in operational mode.

Answer

Privileged mode

Answer

Configuration mode

Answer

Exclusive configuration mode

Question 6

In a dual Routing Engine (RE) setup, an engineer commits a configuration change that should be applied to both REs synchronously. What is the correct command to ensure both REs receive the same configuration immediately?

Accepted Answer

commit synchronize. The 'commit synchronize' command commits the configuration on the master Routing Engine and then automatically copies and commits the same configuration to the backup RE, ensuring both REs have identical active configurations immediately. This is the standard Junos method for synchronizing configurations in a dual-RE chassis.

Answer

commit confirmed

Answer

commit check synchronize

Answer

commit and-quit

Question 7

Refer to the exhibit. An administrator needs to ensure that all emergency (emerg) messages are logged to the console. Based on the configuration shown, which statement is correct?

Accepted Answer

Emergency messages are logged to all destinations.. The configuration shown includes the 'any' facility and 'emerg' severity for the console, file, and remote host destinations. In JUNOS, when a severity level is set for a syslog destination, all messages of that severity and higher are logged. Since 'emerg' is the highest severity, it applies to all configured destinations, not just one.

Answer

Emergency messages are logged to the console only.

Answer

Emergency messages are logged only to the file 'messages'.

Answer

Emergency messages are logged only to the remote host.

Question 8

A route learned via BGP appears as 'hidden' in the routing table. Which condition is most likely the cause?

Accepted Answer

The BGP next-hop is unreachable. In JUNOS, a BGP route is marked as 'hidden' in the routing table when the next-hop address is not reachable via any active route in the inet.0 table. This is a fundamental BGP path selection prerequisite: the next-hop must be resolvable (typically via an IGP or static route) for the route to be considered active and installed.

Answer

The BGP route has a higher AS path length than another route

Answer

The BGP route has been rejected by a policy

Answer

The BGP local preference is too high

Question 9

A network engineer sees an unknown unicast flood on a Juniper EX switch. Which mechanism is most effective at reducing such floods?

Accepted Answer

Enable storm control for unknown unicast traffic.. Unknown unicast flooding occurs when a switch does not have a MAC address entry for a destination, causing it to flood the frame out of all ports in the VLAN except the ingress port. Storm control for unknown unicast traffic (set using `set ethernet-switching-options storm-control interface <interface> unknown-unicast`) directly limits the rate of such flooded traffic, preventing excessive bandwidth consumption. This is the most effective mechanism because it specifically targets and rate-limits unknown unicast floods without altering MAC learning or aging behavior.

Answer

Configure static MAC addresses for all endpoints.

Answer

Increase the MAC address table aging time.

Answer

Disable MAC learning on trunk interfaces.

Question 10

You are a network engineer for a company that uses two Juniper routers, R1 and R2, connected via an Ethernet link. R1 and R2 are running OSPF in the same area, and R2 also has an eBGP session with a service provider to reach the internet. On R1, you have configured a static route to the subnet 172.16.10.0/24 with a next-hop of 192.168.1.2, which is the IP address of R2's interface facing R1. You have verified that the static route is configured correctly in the configuration, but traffic from R1 to 172.16.10.0/24 is not being forwarded. You check the routing table on R1 and see that the static route is present but marked as 'hidden'. You also notice that R1 has an OSPF-learned route to 192.168.1.0/30 (the link between R1 and R2) with a cost of 1. What is the most appropriate next troubleshooting step?

Accepted Answer

Check if the next-hop IP 192.168.1.2 is reachable via the directly connected interface.. A static route becomes hidden in Juniper's routing table when the next-hop is considered unreachable. Although R1 has an OSPF-learned route to the subnet 192.168.1.0/30, the router performs a recursive lookup to ensure the next-hop IP 192.168.1.2 is reachable via a directly connected interface or a valid route. In this case, the next-hop is directly connected, so the most likely cause is that the interface is down, or there is an ARP resolution issue, or a firewall filter blocking ARP. Option D directs you to check if the next-hop is reachable via the directly connected interface, which is the appropriate first troubleshooting step. Option A is incorrect because disabling eBGP on R2 does not affect R1's static route next-hop reachability. Option B is incorrect because lowering preference would not resolve a hidden route; hidden routes are not considered for forwarding regardless of preference. Option C is incorrect because making the route more specific does not address the reachability issue.

Answer

Disable the eBGP session on R2 to remove the BGP routes from the routing table.

Answer

Increase the static route's preference to a lower value (e.g., 4).

Answer

Configure a more specific static route to 172.16.10.0/24 with a mask of /25.