JN0-106 User Interfaces Practice Test 6 — 15 Questions

Question 1

A junior network engineer is learning JunOS CLI and wants to view the last 10 lines of the system log file. They log into the device and type 'show log messages | last 10'. They receive an error: 'unknown pipe command'. Which pipe command should they use instead?

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

Accepted Answer

| tail 10. In JunOS CLI, the pipe command to display the last N lines of output is '| tail N', not '| last N'. The 'tail' command filters the output to show only the final lines, analogous to the Unix 'tail' utility. Option D is correct because '| tail 10' will show the last 10 lines of the system log file.

Answer

| last 10

Answer

| display 10

Answer

| head 10

Question 2

A network engineer wants to view the OSPF log entries in real time. They type 'show log messages | match ospf' and get output, but it does not update. What should they do to see real-time updates of OSPF log entries?

Accepted Answer

Use 'monitor start messages | match ospf'. The 'monitor start messages' command in Junos OS enables real-time streaming of syslog messages to the terminal, similar to 'tail -f' on a log file. Piping the output through '| match ospf' filters the live feed to show only OSPF-related entries. In contrast, 'show log messages' is a one-time snapshot that does not update automatically.

Answer

Use 'show log messages | tail'

Answer

Use 'monitor traffic interface ge-0/0/0'

Answer

Use 'request system syslog'

Question 3

Which TWO statements about the Junos CLI are correct?

Accepted Answer

The pipe character (|) can be used to filter command output.. The pipe character (|) allows filtering command output, such as using `| match` or `| except`. Option C is correct because the `run` command enables execution of operational mode commands while in configuration mode, e.g., `run show interfaces`. Option A is incorrect because `commit confirmed` temporarily activates the configuration and requires a subsequent `commit` to make it permanent; otherwise, it rolls back. Option D is incorrect because `set cli screen-length 0` disables paging (i.e., terminal pausing), not command-line editing. Option E is incorrect because `rollback 0` reverts to the most recently committed configuration, not the previous one; `rollback 1` reverts to the configuration before the last commit.

Answer

The `commit confirmed` command saves the configuration permanently.

Answer

The `set cli screen-length 0` command disables command-line editing features.

Answer

The `rollback 0` command reverts to the previous committed configuration.

Question 4

Refer to the exhibit. The interface ge-0/0/0 is configured as shown, but the interface is operationally down. Which command would provide the most detailed information about the interface status and errors?

Accepted Answer

show interfaces ge-0/0/0 extensive. `show interfaces ge-0/0/0 extensive` provides the most detailed operational information, including error counters, physical state, and protocol details. Option A (`show interfaces ge-0/0/0`) shows a brief summary. Option B (`show configuration interfaces ge-0/0/0`) shows the configuration, not operational status. Option C (`show interfaces ge-0/0/0 terse`) shows a condensed output. Therefore, extensive is the best choice to diagnose why the interface is down.

Answer

show interfaces ge-0/0/0

Answer

show configuration interfaces ge-0/0/0

Answer

show interfaces ge-0/0/0 terse

Question 5

Tom is a junior network engineer who recently joined a service provider. He is tasked with configuring a new BGP session on an MX240 router to peer with a customer. He accesses the router via SSH and enters configuration mode using the `configure` command. He then navigates to `edit protocols bgp` and begins configuring. He sets the local AS number, adds a group named 'CUSTOMER-A', and specifies the peer IP address 192.0.2.2. After completing the configuration, he attempts to commit by typing `commit`. The system returns a syntax error and indicates that the configuration is invalid. Tom is unsure what went wrong and wants to identify the error before making any changes. What should Tom do next?

Accepted Answer

Issue the `commit check` command to validate the candidate configuration syntax.. `commit check` validates the candidate configuration syntax without committing, and will point out the specific error that caused the syntax error. Option B (`show | compare`) shows changes but does not check syntax. Option C displays the active (committed) configuration, not the candidate. Option D simply re-enters the hierarchy, which does not help identify the error.

Answer

Issue the `show | compare` command to see the differences from the previous committed configuration.

Answer

Issue the `run show configuration protocols bgp` command to display the current active configuration.

Answer

Issue the `edit protocols bgp` command again to re-enter the hierarchy and review the settings.

Question 6

During troubleshooting, an engineer needs to view real-time logging messages on a Junos device. Which command should be used?

Accepted Answer

monitor start messages. The 'monitor start messages' command enables real-time, tail-like display of the /var/log/messages log file on a Junos device, allowing the engineer to view new log entries as they are generated. This is the correct command for live troubleshooting because it continuously updates the terminal with incoming syslog messages, unlike static file viewing commands.

Answer

file show /var/log/messages

Answer

show log messages

Answer

traceoptions

Question 7

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 8

A network engineer needs to view the operational status of all interfaces on a Junos device, including those that are disabled. Which command should be used?

Accepted Answer

show interfaces terse. The 'show interfaces' command displays detailed information for all interfaces, including those that are administratively disabled. However, 'show interfaces terse' provides a concise, one-line-per-interface summary that is more efficient for quickly viewing the operational status of all interfaces, including disabled ones. For the JNCIA exam, 'show interfaces terse' is the recommended command for this purpose because it offers a clear and compact overview of interface status across the device.

Answer

show interfaces

Answer

show configuration interfaces

Answer

monitor interface traffic

Question 9

You are a network engineer for a company that has just deployed a Juniper SRX firewall in a branch office. The device has multiple interfaces: ge-0/0/0 connected to the internet, ge-0/0/1 connected to the internal LAN (192.168.1.0/24), and ge-0/0/2 connected to a DMZ (10.0.0.0/24). After initial configuration, you attempt to ping from the SRX to a server on the internet (8.8.8.8) but receive no response. You also notice that internal users can access the internet. You have verified the routing table shows a default route via ge-0/0/0. The security policies appear correct. You suspect the issue is related to interface configuration. What is the most likely cause and the correct course of action?

Accepted Answer

The interface ge-0/0/0 is missing the 'host-inbound-traffic' configuration under its security zone; you should add the appropriate system services under the zone.. The SRX can ping internal hosts but not the internet because the interface ge-0/0/0 is in the untrust zone, which by default blocks all inbound traffic, including pings originated from the device itself. The 'host-inbound-traffic' configuration under the security zone allows system services such as ping, SSH, and SNMP to be received on that interface. Without it, even though the routing table and security policies are correct, the SRX will drop its own outbound ICMP echo requests before they can be sent, or drop the replies if they are treated as inbound traffic.

Answer

The security policy from the trust zone to the untrust zone is blocking traffic; you should create a policy allowing all traffic from the SRX itself.

Answer

The interface ge-0/0/0 has an incorrect MAC address; you should clear the ARP cache.

Answer

The default route is missing or incorrect; you should add a default route via the internet gateway IP.

Question 10

You are a junior network engineer at a company that uses Juniper MX routers. You are troubleshooting a connectivity issue on a branch router. The branch router has two upstream links to the corporate network: ge-0/0/0 (10.1.1.1/30, connected to core router A) and ge-0/0/1 (10.1.1.5/30, connected to core router B). The branch router runs OSPF and has a default route learned from both upstream routers. The routing table shows two equal-cost default routes via both next hops. However, traffic from the branch to the corporate network is experiencing intermittent high latency and some packet loss. You suspect that asymmetric routing is causing issues because the return traffic is not following the same path. You want to influence the router to prefer one upstream link for all traffic to the corporate network. You have decided to adjust the OSPF metric on the branch router to make the link to core router A more preferred. You are in configuration mode on the branch router. Which single configuration change will accomplish this goal?

Accepted Answer

set protocols ospf area 0 interface ge-0/0/1 metric 200. Setting the OSPF metric on interface ge-0/0/1 to a higher value (200) increases the cost of that link, making the default route via ge-0/0/0 (which retains the default OSPF metric of 1 on a Gigabit Ethernet interface) more preferred. This influences the branch router to use the lower-cost path through core router A for all traffic to the corporate network, resolving asymmetric routing issues.

Answer

set interfaces ge-0/0/1 unit 0 family inet cost 200

Answer

set protocols ospf area 0 interface ge-0/0/1 passive

Answer

set interfaces lo0 unit 0 family inet address 10.0.0.1/32 metric 100

Question 11

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 12

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 13

Which THREE modes can be used to enter configuration mode in Junos? (Choose three.)

Accepted Answer

configure private. 'configure private' creates a private configuration session that isolates candidate changes from other users, allowing multiple users to stage changes simultaneously without interference. This mode is one of the three standard configuration modes in Junos, alongside exclusive and shared.

Answer

configure static

Answer

configure dynamic

Question 14

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 15

A network administrator accidentally deleted a vital part of the configuration while in configuration mode. They need to revert to the previous configuration without losing recent changes that are correct. Which action should they take?

Accepted Answer

rollback 0. The 'rollback 0' command reverts the candidate configuration to the most recently committed configuration (the current active configuration), discarding any uncommitted changes. This allows the administrator to undo the accidental deletion without affecting any recently committed correct changes, as those are already part of the active configuration. Option B, 'rollback 1', would revert to the previous commit, which could remove recently committed correct changes if they were made in the most recent commit. Therefore, 'rollback 0' is the safer choice when you want to preserve correct changes that have already been committed.

Answer

deactivate

Answer

rollback 1

Answer

delete