Practice Free JN0-280 Exam Online Questions
Question #11
Layer 2 interfaces operate in which two modes? (Choose two.)
- A . Access
- B . Modular
- C . Trunk
- D . Tagged
Correct Answer: A, C
A, C
Explanation:
Comprehensive Detailed Step by Step Explanation with all Juniper Data Center References Layer 2 interfaces on a switch operate in two key modes: Access and Trunk.
Step-by-Step Breakdown:
Access Mode:
Access ports are used to connect end devices, like PCs or servers, and they are assigned to a single VLAN. These interfaces handle untagged traffic and do not pass VLAN tags. Example: A port assigned to VLAN 10 will only handle traffic for that VLAN.
Trunk Mode:
Trunk ports are used to connect switches or other networking devices that need to handle traffic from multiple VLANs. Trunk interfaces carry tagged traffic, allowing multiple VLANs to traverse the same physical link.
Trunk ports typically use 802.1Q VLAN tagging to differentiate between VLANs.
Juniper
Reference: Access and Trunk Ports: Juniper switches use these modes to manage VLAN traffic at Layer 2, with access ports handling untagged traffic and trunk ports handling tagged traffic from multiple VLANs.
A, C
Explanation:
Comprehensive Detailed Step by Step Explanation with all Juniper Data Center References Layer 2 interfaces on a switch operate in two key modes: Access and Trunk.
Step-by-Step Breakdown:
Access Mode:
Access ports are used to connect end devices, like PCs or servers, and they are assigned to a single VLAN. These interfaces handle untagged traffic and do not pass VLAN tags. Example: A port assigned to VLAN 10 will only handle traffic for that VLAN.
Trunk Mode:
Trunk ports are used to connect switches or other networking devices that need to handle traffic from multiple VLANs. Trunk interfaces carry tagged traffic, allowing multiple VLANs to traverse the same physical link.
Trunk ports typically use 802.1Q VLAN tagging to differentiate between VLANs.
Juniper
Reference: Access and Trunk Ports: Juniper switches use these modes to manage VLAN traffic at Layer 2, with access ports handling untagged traffic and trunk ports handling tagged traffic from multiple VLANs.
Question #12
In the context of data center networking, what is the primary purpose of an Underlay Network?
- A . To provide a physical infrastructure for an Overlay Network.
- B . To handle external network connections exclusively.
- C . To facilitate virtual machine migrations.
- D . To encrypt data traffic between servers.
Correct Answer: A
Question #13
Which OSPF packet types are used to establish and maintain neighbor relationships? (Choose two)
- A . Hello packets
- B . Database Description packets
- C . Link State Request packets
- D . Link State Update packets
Correct Answer: AB
Question #14
Which statement is correct about aggregate routes?
- A . The default next hop is discard.
- B . The default next hop is readvertise.
- C . The default next hop is resolve.
- D . The default next hop is reject.
Correct Answer: D
D
Explanation:
An aggregate route is a summarized route that is created by combining multiple specific routes into a single, broader route. In Junos OS, when an aggregate route is configured, its default next hop is set to reject.
Step-by-Step
Aggregate Route:
Aggregate routes are used to reduce the size of routing tables by representing a collection of more specific routes with a single summary route. They help improve routing efficiency and scalability, especially in large networks.
Default Next Hop Behavior:
When you configure an aggregate route in Junos OS, it has a reject next hop by default.
The reject next hop means that if a packet matches the aggregate route but there is no more specific route in the routing table for that destination, the packet will be discarded, and an ICMP "destination unreachable" message is sent to the source.
This behavior helps to prevent routing loops and ensures that traffic isn’t forwarded to destinations for which there is no valid route.
Modifying Next Hop:
If needed, the next hop behavior of an aggregate route can be changed to discard (which silently drops the packet) or to another specific next hop. However, by default, the next hop is set to reject. Juniper Reference: Junos Command: set routing-options aggregate route <route> reject to configure an aggregate route with a reject next hop.
Verification: Use show route to verify the presence and behavior of aggregate routes.
D
Explanation:
An aggregate route is a summarized route that is created by combining multiple specific routes into a single, broader route. In Junos OS, when an aggregate route is configured, its default next hop is set to reject.
Step-by-Step
Aggregate Route:
Aggregate routes are used to reduce the size of routing tables by representing a collection of more specific routes with a single summary route. They help improve routing efficiency and scalability, especially in large networks.
Default Next Hop Behavior:
When you configure an aggregate route in Junos OS, it has a reject next hop by default.
The reject next hop means that if a packet matches the aggregate route but there is no more specific route in the routing table for that destination, the packet will be discarded, and an ICMP "destination unreachable" message is sent to the source.
This behavior helps to prevent routing loops and ensures that traffic isn’t forwarded to destinations for which there is no valid route.
Modifying Next Hop:
If needed, the next hop behavior of an aggregate route can be changed to discard (which silently drops the packet) or to another specific next hop. However, by default, the next hop is set to reject. Juniper Reference: Junos Command: set routing-options aggregate route <route> reject to configure an aggregate route with a reject next hop.
Verification: Use show route to verify the presence and behavior of aggregate routes.
Question #15
Referring to the exhibit, how many milliseconds will pass before the BGP neighbor is considered dead?
- A . 1000ms
- B . 9000ms
- C . 2000ms
- D . 3000ms
Correct Answer: D
Question #16
What is the behavior of the default export policy for OSPF?
- A . Accept all routes.
- B . Reject all routes.
- C . Redistribute all routes.
- D . Forward all routes.
Correct Answer: B
B
Explanation:
In Junos, the default export policy for OSPF is to reject all routes from being exported.
Step-by-Step Breakdown:
Default Export Policy:
By default, OSPF in Junos does not export any routes to other routing protocols or neighbors. This is a safety mechanism to prevent unintended route advertisements. Custom Export Policies:
If you need to export routes, you must create a custom export policy that explicitly defines which routes to advertise.
Example: You can create an export policy to redistribute static or connected routes into OSPF.
Juniper
Reference: OSPF Export Behavior: In Juniper devices, the default policy for OSPF is to reject route advertisements unless explicitly configured otherwise through custom policies.
B
Explanation:
In Junos, the default export policy for OSPF is to reject all routes from being exported.
Step-by-Step Breakdown:
Default Export Policy:
By default, OSPF in Junos does not export any routes to other routing protocols or neighbors. This is a safety mechanism to prevent unintended route advertisements. Custom Export Policies:
If you need to export routes, you must create a custom export policy that explicitly defines which routes to advertise.
Example: You can create an export policy to redistribute static or connected routes into OSPF.
Juniper
Reference: OSPF Export Behavior: In Juniper devices, the default policy for OSPF is to reject route advertisements unless explicitly configured otherwise through custom policies.
Question #17
In OSPF, which command is commonly used to monitor neighbor relationships?
- A . show ip ospf neighbors
- B . show ospf database
- C . show ip route ospf
- D . show ospf interfaces
Correct Answer: A
Question #18
In the Junos OS, which feature is used to create an alternate next hop with a unique preference for a static route?
- A . Preference
- B . Resolve
- C . Next-hop
- D . Qualified-next-hop
Correct Answer: D
D
Explanation:
In Junos OS, the qualified-next-hop feature is used to specify an alternate next hop for a static route, along with a unique preference value.
Step-by-Step Breakdown:
Qualified-Next-Hop:
A qualified-next-hop allows you to define multiple next hops for a static route, each with its own preference. This provides flexibility by allowing the router to choose the best available next hop based on reachability and preference.
Use Case:
If the primary next hop becomes unreachable, the router can automatically switch to the alternate next hop defined by the qualified-next-hop with a higher preference value.
Command Example:
set routing-options static route 10.10.10.0/24 qualified-next-hop 192.168.1.1 preference 5 set routing-options static route 10.10.10.0/24 qualified-next-hop 192.168.1.2 preference 10
Preference:
The next hop with the lowest preference is chosen first. If it becomes unavailable, the router will use
the higher preference next hop.
Juniper
Reference: Qualified-Next-Hop: This feature is used to configure backup or alternate next hops for static routes in Juniper devices.
D
Explanation:
In Junos OS, the qualified-next-hop feature is used to specify an alternate next hop for a static route, along with a unique preference value.
Step-by-Step Breakdown:
Qualified-Next-Hop:
A qualified-next-hop allows you to define multiple next hops for a static route, each with its own preference. This provides flexibility by allowing the router to choose the best available next hop based on reachability and preference.
Use Case:
If the primary next hop becomes unreachable, the router can automatically switch to the alternate next hop defined by the qualified-next-hop with a higher preference value.
Command Example:
set routing-options static route 10.10.10.0/24 qualified-next-hop 192.168.1.1 preference 5 set routing-options static route 10.10.10.0/24 qualified-next-hop 192.168.1.2 preference 10
Preference:
The next hop with the lowest preference is chosen first. If it becomes unavailable, the router will use
the higher preference next hop.
Juniper
Reference: Qualified-Next-Hop: This feature is used to configure backup or alternate next hops for static routes in Juniper devices.
Question #19
What is the default Junos behavior of access ports?
- A . Allow only untagged traffic
- B . Allow only tagged traffic
- C . Allow both tagged and untagged traffic
- D . Allow a maximum of 80 percent untagged traffic
Correct Answer: A
Question #20
In the context of Link Aggregation Groups (LAG), what is the primary purpose of LACP?
- A . To provide a method for encrypting data packets
- B . To dynamically manage the bundling of several physical ports
- C . To reduce the speed of data transfer
- D . To increase the error rate in data transmission
Correct Answer: B