Sample questions
Juniper Networks Certified Associate Junos JNCIA-Junos practice questions
A junior engineer needs to collect a snapshot of the current system state, including routing tables, interfaces, and configuration, for a support ticket. Which command achieves this?
Trap 1: show configuration
Only shows configuration, not operational state.
Trap 2: show interfaces
Only shows interface details.
Trap 3: show route
Only shows routing table.
- A
show configuration
Why wrong: Only shows configuration, not operational state.
- B
show interfaces
Why wrong: Only shows interface details.
- C
request support information
Gathers comprehensive system data for troubleshooting.
- D
show route
Why wrong: Only shows routing table.
A network engineer is troubleshooting a connectivity issue and wants to see the active routes in the routing table. Which Junos CLI command should they use?
Trap 1: show log messages
Shows system log messages.
Trap 2: show configuration
Shows the configuration, not routing table.
Trap 3: show interface
Shows interface status, not routing table.
- A
show log messages
Why wrong: Shows system log messages.
- B
show configuration
Why wrong: Shows the configuration, not routing table.
- C
show interface
Why wrong: Shows interface status, not routing table.
- D
show route
Displays the routing table.
You are the network engineer for a mid-sized enterprise with a Juniper MX router running Junos. The router has two uplinks to the internet: one to ISP-A via ge-0/0/0 (10.0.0.1/30) and one to ISP-B via ge-0/0/1 (10.0.0.5/30). You have configured static default routes to both ISPs: one to 10.0.0.2 and one to 10.0.0.6. Both routes have the same preference (default 5) and metric. You enabled ECMP to load-balance outbound traffic. After testing, you notice that all traffic is being sent only to ISP-A, and none to ISP-B. You verify that both interfaces are up and that the next-hop addresses are reachable. You check the routing table and see both routes are active but with different next-hop counts. What is the most likely cause of the traffic not being load-balanced?
Trap 1: ECMP is not enabled in the forwarding-options.
ECMP is enabled, but the issue is next-hop count.
Trap 2: The route to ISP-B is not active.
Both routes are active.
Trap 3: Hash-based load balancing requires per-packet configuration.
Hash-based is default; per-packet is not typical.
- A
One of the static routes resolves to multiple next hops, causing imbalance.
If one route resolves to multiple next hops, it may appear as multiple routes, skewing load balancing.
- B
ECMP is not enabled in the forwarding-options.
Why wrong: ECMP is enabled, but the issue is next-hop count.
- C
The route to ISP-B is not active.
Why wrong: Both routes are active.
- D
Hash-based load balancing requires per-packet configuration.
Why wrong: Hash-based is default; per-packet is not typical.
Which TWO attributes are used by Junos to select the active route among multiple routes to the same destination?
Trap 1: Protocol type
Protocol type is factored into preference.
Trap 2: Next hop address
Next hop is not used for selection.
Trap 3: AS path length
AS path is used in BGP but not in general route selection.
- A
Metric
Lower metric is preferred when preference is equal.
- B
Preference
Lower preference is preferred.
- C
Protocol type
Why wrong: Protocol type is factored into preference.
- D
Next hop address
Why wrong: Next hop is not used for selection.
- E
AS path length
Why wrong: AS path is used in BGP but not in general route selection.
What is the default preference of a direct route in Junos?
Trap 1: 10
OSPF internal routes have preference 10.
Trap 2: 5
Static routes have preference 5.
Trap 3: 15
No standard protocol uses preference 15.
- A
0
Direct routes have preference 0.
- B
10
Why wrong: OSPF internal routes have preference 10.
- C
5
Why wrong: Static routes have preference 5.
- D
15
Why wrong: No standard protocol uses preference 15.
A router has two routes to the same destination: one with preference 10 and metric 5, and another with preference 15 and metric 3. Which route will be installed in the forwarding table?
Trap 1: The route with metric 3.
Metric is secondary to preference.
Trap 2: Neither route is installed.
One route is installed.
Trap 3: Both routes are installed if ECMP is enabled.
ECMP requires equal preference and metric.
- A
The route with preference 10.
Preference is the primary selection criterion.
- B
The route with metric 3.
Why wrong: Metric is secondary to preference.
- C
Neither route is installed.
Why wrong: One route is installed.
- D
Both routes are installed if ECMP is enabled.
Why wrong: ECMP requires equal preference and metric.
A network engineer is designing a redundant network with two Juniper routers running VRRP. The virtual IP address is 10.0.0.1. Both routers are configured as VRRP group 1. What is the purpose of the 'priority' parameter in VRRP configuration?
Trap 1: It sets the interval for VRRP advertisements.
Advertisement interval is configured separately with the 'advertise-interval' parameter.
Trap 2: It determines the virtual MAC address.
The virtual MAC address is based on the VRRP group ID, not priority.
Trap 3: It changes the virtual IP address.
The virtual IP address is configured directly and is not affected by priority.
- A
It sets the interval for VRRP advertisements.
Why wrong: Advertisement interval is configured separately with the 'advertise-interval' parameter.
- B
It determines the master router election.
Higher priority increases the chance of becoming the master.
- C
It determines the virtual MAC address.
Why wrong: The virtual MAC address is based on the VRRP group ID, not priority.
- D
It changes the virtual IP address.
Why wrong: The virtual IP address is configured directly and is not affected by priority.
Which TWO statements correctly describe the behavior of the 'commit confirmed' command in Junos?
Trap 1: The default confirmation timeout is 5 minutes.
Incorrect: The default timeout is 10 minutes.
Trap 2: It requires a reboot to revert to the previous configuration.
Incorrect: No reboot is required; rollback is immediate.
Trap 3: It stages the configuration in the candidate configuration but does…
Incorrect: The configuration is applied immediately upon commit.
- A
The confirmation timeout can be modified by specifying a number of minutes.
Correct: The timeout can be set from 1 to 65535 minutes.
- B
The default confirmation timeout is 5 minutes.
Why wrong: Incorrect: The default timeout is 10 minutes.
- C
It requires a reboot to revert to the previous configuration.
Why wrong: Incorrect: No reboot is required; rollback is immediate.
- D
It activates the configuration and schedules an automatic rollback unless confirmed.
Correct: 'commit confirmed' applies the configuration and sets a timer for automatic rollback.
- E
It stages the configuration in the candidate configuration but does not apply it until confirmed.
Why wrong: Incorrect: The configuration is applied immediately upon commit.
Based on the exhibit, which protocol is enabled on interface ge-0/0/0.0?
Exhibit
Refer to the exhibit.
user@router> show interfaces ge-0/0/0.0
Logical interface ge-0/0/0.0 (Index 70) (SNMP ifIndex 521)
Flags: Up SNMP-Traps 0x4004000 Encapsulation: ENET2
Input packets : 1500
Output packets: 1200
Security: Zone: Trust
Allowed host-inbound traffic : any-service
Protocols:
inet:
10.0.0.1/24
iso:
mpls:
Maximum labels: 3
multiservice:
encapsulation: ethernet-cccTrap 1: IS-IS
Not shown in the exhibit.
Trap 2: BGP
Not shown in the exhibit.
Trap 3: OSPF
Not shown in the exhibit.
- A
IS-IS
Why wrong: Not shown in the exhibit.
- B
BGP
Why wrong: Not shown in the exhibit.
- C
MPLS
Correct: MPLS is listed under Protocols.
- D
OSPF
Why wrong: Not shown in the exhibit.
A network engineer is troubleshooting a reachability issue between two directly connected routers. Both routers have IP addresses configured on their interfaces and the interfaces are up. Which command would the engineer use to verify the routing table entry for the remote network?
Trap 1: show interfaces terse
Shows interface status and IP addresses, not the routing table.
Trap 2: show configuration interfaces
Shows the interface configuration, not the operational routing table.
Trap 3: show arp
Shows the ARP cache, not the routing table.
- A
show route
Displays the routing table, including directly connected and learned routes.
- B
show interfaces terse
Why wrong: Shows interface status and IP addresses, not the routing table.
- C
show configuration interfaces
Why wrong: Shows the interface configuration, not the operational routing table.
- D
show arp
Why wrong: Shows the ARP cache, not the routing table.
You are managing a small enterprise network with one Juniper router and two switches. The router connects to an ISP via ge-0/0/0 and to the internal network via ge-0/0/1. The internal network uses the 192.168.1.0/24 subnet. You need to configure a default route on the router to send all Internet-bound traffic to the ISP gateway at 203.0.113.1. You also want to ensure that internal hosts can reach the Internet. After configuring the default route, you test connectivity from a host on the internal network to an external website, but the ping fails. You verify that the host has an IP address of 192.168.1.100/24 and a default gateway of 192.168.1.1 (the router's internal interface). On the router, you run 'show route 0.0.0.0/0' and see the default route active. You also run 'ping 203.0.113.1' from the router and it succeeds. However, pinging from the host to the ISP gateway fails. What is the most likely cause?
Trap 1: DNS resolution is failing on the host.
The ping test used an IP address, not a hostname, so DNS is not involved.
Trap 2: The host's default gateway is incorrectly configured.
The host's default gateway is 192.168.1.1, which is correct.
Trap 3: The default route is not active on the router.
The exhibit shows the default route is active.
- A
DNS resolution is failing on the host.
Why wrong: The ping test used an IP address, not a hostname, so DNS is not involved.
- B
The host's default gateway is incorrectly configured.
Why wrong: The host's default gateway is 192.168.1.1, which is correct.
- C
The default route is not active on the router.
Why wrong: The exhibit shows the default route is active.
- D
Proxy ARP is not enabled on the router's internal interface.
Without proxy ARP, the router does not respond to ARP requests for the ISP gateway, so the host cannot resolve the next-hop MAC.
Which TWO statements correctly describe Junos configuration hierarchy and management?
Trap 1: The 'deactivate' command permanently removes a configuration…
'deactivate' disables the statement but keeps it in the candidate; it can be reactivated.
Trap 2: The 'set' command in configuration mode directly modifies the…
'set' modifies the candidate configuration, not the active one.
Trap 3: In operational mode, the 'show' command displays the candidate…
Operational mode 'show configuration' displays the active configuration, not candidate.
- A
The 'deactivate' command permanently removes a configuration statement from the candidate.
Why wrong: 'deactivate' disables the statement but keeps it in the candidate; it can be reactivated.
- B
The 'load merge' command imports configuration from a file and merges it with the current candidate configuration.
'load merge' combines the file content with the existing candidate.
- C
The candidate configuration is a separate copy that does not affect the active configuration until committed.
Candidate config is independent and only becomes active after commit.
- D
The 'set' command in configuration mode directly modifies the active configuration.
Why wrong: 'set' modifies the candidate configuration, not the active one.
- E
In operational mode, the 'show' command displays the candidate configuration.
Why wrong: Operational mode 'show configuration' displays the active configuration, not candidate.
Which TWO statements correctly describe the behavior of the Junos CLI operational mode?
Trap 1: Command options are enclosed in curly braces { }.
Curly braces are for configuration display, not CLI options.
Trap 2: Commands must be entered in full; abbreviation is not allowed.
Commands can be abbreviated to a unique prefix.
Trap 3: You can commit configuration changes directly.
Commit is done in configuration mode, not operational mode.
- A
Commands such as show and ping are available.
Operational mode provides show and ping commands.
- B
Command options are enclosed in curly braces { }.
Why wrong: Curly braces are for configuration display, not CLI options.
- C
Commands must be entered in full; abbreviation is not allowed.
Why wrong: Commands can be abbreviated to a unique prefix.
- D
You can commit configuration changes directly.
Why wrong: Commit is done in configuration mode, not operational mode.
- E
The CLI uses a hierarchical command structure.
Junos CLI is hierarchical with different levels.
An engineer needs to apply a configuration change to the Junos device that must survive a reboot. Which configuration mode command should be used to save the changes?
Trap 1: commit confirmed
'commit confirmed' requires a confirming commit within the rollback time or the configuration rolls back.
Trap 2: commit synchronize
'commit synchronize' is used on dual RE systems to copy the config to both REs but does not affect persistence beyond a normal commit.
Trap 3: commit check
'commit check' validates the configuration syntax but does not save it.
- A
commit
'commit' saves the candidate configuration into the active configuration, which survives a reboot.
- B
commit confirmed
Why wrong: 'commit confirmed' requires a confirming commit within the rollback time or the configuration rolls back.
- C
commit synchronize
Why wrong: 'commit synchronize' is used on dual RE systems to copy the config to both REs but does not affect persistence beyond a normal commit.
- D
commit check
Why wrong: 'commit check' validates the configuration syntax but does not save it.
Your company operates a dual-homed network with two Juniper MX routers (R1 and R2) each connected to a different ISP. R1 uses BGP to receive a default route from ISP-A (preference 170), and R2 uses BGP to receive a default route from ISP-B (preference 170). Additionally, both routers have a static default route pointing to a local next-hop (192.0.2.1) with preference 5 for backup. R1 and R2 are connected via an internal link (10.0.0.0/30) and run OSPF to exchange internal routes. You notice that traffic from internal hosts is always exiting via R1's ISP-A link, even when R1's BGP session to ISP-A goes down. The OSPF routes are preferred. You want traffic to fail over to R2's ISP-B link when R1 loses its BGP default. Which configuration change should you make?
Trap 1: Increase the preference of the BGP default routes to 180 so that…
This would make the static default always active, preventing failover between ISPs.
Trap 2: Configure a routing policy on R2 to reject the default route from…
This would eliminate redundancy.
Trap 3: Remove the static default route and rely on OSPF to propagate a…
Without any static default, if both BGP sessions fail, there is no default route.
- A
Increase the preference of the BGP default routes to 180 so that the static default is always preferred.
Why wrong: This would make the static default always active, preventing failover between ISPs.
- B
Configure a routing policy on R2 to reject the default route from ISP-B, forcing all traffic through R1.
Why wrong: This would eliminate redundancy.
- C
Remove the static default route and rely on OSPF to propagate a default route from the router with the active BGP session.
Why wrong: Without any static default, if both BGP sessions fail, there is no default route.
- D
Configure the static default route with a preference of 180 so that the BGP default routes (pref 170) are preferred when available.
This ensures BGP default is used when up, and OSPF routes to R2's default become active when R1's BGP is down.
Match each Junos system log severity level to its meaning.
Drag a concept onto its matching description — or click a concept then click the description.
System is unusable
Immediate action needed
Critical conditions
Error conditions
Warning conditions
Which THREE statements are true about commit operations in Junos OS?
Trap 1: The 'commit confirmed' command immediately discards changes if not…
It schedules a rollback; changes are not immediately discarded.
Trap 2: The 'commit' command always requires 'commit synchronize' when…
'commit synchronize' is used only when you want to synchronize configurations; 'commit' alone commits only on the local RE.
- A
The 'commit confirmed' command immediately discards changes if not confirmed.
Why wrong: It schedules a rollback; changes are not immediately discarded.
- B
Multiple users can make configuration changes simultaneously, but only one can commit at a time.
Junos uses a lock to serialize commits.
- C
The 'commit check' command validates the configuration syntax without activating it.
'commit check' verifies syntax and semantics without committing.
- D
The 'commit confirmed' command allows a rollback to the previous configuration if not confirmed within the timeout period.
This is the purpose of 'commit confirmed'.
- E
The 'commit' command always requires 'commit synchronize' when using dual Routing Engines.
Why wrong: 'commit synchronize' is used only when you want to synchronize configurations; 'commit' alone commits only on the local RE.
A network engineer is troubleshooting connectivity between two directly connected Juniper routers. The interface on Router A shows 'up' but no packets are being received from Router B. Which command should the engineer use on Router A to check if the interface is expecting to receive a specific encapsulation type?
Trap 1: show interfaces extensive
Shows detailed interface info but not specifically encapsulation expectation.
Trap 2: show configuration interfaces
Shows configuration, not current encapsulation status.
Trap 3: monitor traffic interface
Captures packets, not encapsulation.
- A
show interfaces extensive
Why wrong: Shows detailed interface info but not specifically encapsulation expectation.
- B
show interfaces terse
Displays interface status and encapsulation type.
- C
show configuration interfaces
Why wrong: Shows configuration, not current encapsulation status.
- D
monitor traffic interface
Why wrong: Captures packets, not encapsulation.
A network administrator is configuring a new subnet for servers that must not communicate with each other directly but must be able to reach a default gateway. Which type of route should be configured on the servers?
Trap 1: Host route for the gateway
Host route is for a single IP, not for reaching all destinations.
Trap 2: Dynamic route via OSPF
Servers typically do not run routing protocols.
Trap 3: Static route to each other server
Unnecessary and would allow direct communication.
- A
Host route for the gateway
Why wrong: Host route is for a single IP, not for reaching all destinations.
- B
Default route pointing to the gateway
Standard for server default gateway configuration.
- C
Dynamic route via OSPF
Why wrong: Servers typically do not run routing protocols.
- D
Static route to each other server
Why wrong: Unnecessary and would allow direct communication.
An engineer is designing a network with two routers connected via a serial link. The link should support multiple logical subinterfaces for different VLANs. Which encapsulation type must be used on the serial interface?
Trap 1: Ethernet
Ethernet is not used on serial interfaces.
Trap 2: PPP
PPP does not support subinterfaces.
Trap 3: HDLC
HDLC is Cisco proprietary and does not support subinterfaces.
- A
Ethernet
Why wrong: Ethernet is not used on serial interfaces.
- B
PPP
Why wrong: PPP does not support subinterfaces.
- C
Frame Relay
Frame Relay supports subinterfaces for multiple logical circuits.
- D
HDLC
Why wrong: HDLC is Cisco proprietary and does not support subinterfaces.
A Juniper router is configured with two static routes to the same destination network, both with the same preference. One route has a metric of 5, the other a metric of 10. Which route will be installed in the routing table?
Trap 1: Neither route is installed because they conflict
Static routes can coexist; the best is chosen.
Trap 2: The route with metric 10 is installed
Higher metric is worse.
Trap 3: Both routes are installed with equal preference
Only the best route is installed.
- A
Neither route is installed because they conflict
Why wrong: Static routes can coexist; the best is chosen.
- B
The route with metric 5 is installed
Lower metric is preferred when preference is equal.
- C
The route with metric 10 is installed
Why wrong: Higher metric is worse.
- D
Both routes are installed with equal preference
Why wrong: Only the best route is installed.
A network engineer needs to check the operational status of all interfaces on a Juniper device. Which command provides a summary of interface status including link state, protocol state, and error counters?
Trap 1: show interfaces
This shows detailed information, not a summary.
Trap 2: show configuration interfaces
This shows the configuration, not operational status.
Trap 3: show interface descriptions
This only displays interface descriptions.
- A
show interfaces
Why wrong: This shows detailed information, not a summary.
- B
show configuration interfaces
Why wrong: This shows the configuration, not operational status.
- C
show interfaces terse
This command displays interface status in a compact format.
- D
show interface descriptions
Why wrong: This only displays interface descriptions.
Refer to the exhibit. How many next hops are configured for the 192.168.1.0/24 route?
Exhibit
Refer to the exhibit.
user@router> show route protocol static
inet.0: 4 destinations, 4 routes (4 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
192.168.1.0/24 *[Static/5] 00:10:00, metric2 0
> to 10.0.0.1 via ge-0/0/0.0
[Static/5] 00:05:00, metric2 0
to 10.0.0.2 via ge-0/0/1.0
192.168.2.0/24 *[Static/5] 00:15:00, metric2 0
> to 10.0.0.1 via ge-0/0/0.0Trap 1: 0
The route has next hops.
Trap 2: 3
Only two next hops are shown.
Trap 3: 1
There are two next-hop entries, not one.
- A
0
Why wrong: The route has next hops.
- B
3
Why wrong: Only two next hops are shown.
- C
1
Why wrong: There are two next-hop entries, not one.
- D
2
The route has two next hops: 10.0.0.1 and 10.0.0.2.
Refer to the exhibit. An engineer configures a new IPv6 address on ge-0/0/0 unit 0 by entering the following commands in configuration mode:
set interfaces ge-0/0/0 unit 0 family inet6 address 2001:db8::2/64 commit
After the commit, the engineer runs 'show interfaces terse ge-0/0/0' and sees only the two original addresses. What is the most likely cause?
Exhibit
Refer to the exhibit.
user@router> show configuration interfaces ge-0/0/0
unit 0 {
family inet {
address 10.0.0.1/24;
}
family inet6 {
address 2001:db8::1/64;
}
}
user@router> show interfaces terse ge-0/0/0
Interface Admin Link Proto Local Remote
ge-0/0/0 up up inet 10.0.0.1/24
inet6 2001:db8::1/64Trap 1: The engineer used 'commit' instead of 'commit confirmed'.
A standard commit is sufficient to apply changes.
Trap 2: Junos only allows one IPv6 address per interface.
Junos supports multiple IPv6 addresses.
Trap 3: The 'set' command requires the 'add' keyword to add a second…
'set' is used to add or change configuration; no 'add' keyword needed.
- A
The engineer used 'commit' instead of 'commit confirmed'.
Why wrong: A standard commit is sufficient to apply changes.
- B
The engineer did not enter configuration mode before running the 'set' command.
'set' is a configuration mode command; in operational mode it would be rejected.
- C
Junos only allows one IPv6 address per interface.
Why wrong: Junos supports multiple IPv6 addresses.
- D
The 'set' command requires the 'add' keyword to add a second address.
Why wrong: 'set' is used to add or change configuration; no 'add' keyword needed.
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