Practice Free JN0-280 Exam Online Questions
Question #21
Fill in the blank: In BGP, a route received from an ___________ peer will not be advertised to another ___________ peer by default.
- A . IBGP, IBGP
- B . EBGP, EBGP
- C . EBGP, IBGP
- D . Static, Dynamic
Correct Answer: A
Question #22
When a MAC limiting violation occurs, the switch performs which two actions by default? (Choose two.)
- A . No logging takes place.
- B . It causes Layer 2 loops.
- C . The port is disabled.
- D . It drops the packet.
Correct Answer: C, D
C, D
Explanation:
When a MAC limiting violation occurs on a Juniper switch, the switch will perform the following actions by default:
Step-by-Step Breakdown:
Port Disabled:
When the number of MAC addresses on an interface exceeds the configured limit, the port is automatically disabled to prevent further violations. This is a protective mechanism to prevent MAC address flooding.
Packet Dropped:
Additionally, packets from the violating MAC address are dropped to prevent any further communication from that address. This ensures that only valid MAC addresses are allowed to communicate through the interface.
Example Configuration:
set ethernet-switching-options secure-access-port interface <interface-name> mac-limit 5
If more than five MAC addresses are learned, the port is disabled, and excess packets are dropped.
Juniper
Reference: MAC Limiting: When the switch detects a MAC limiting violation, it disables the port and drops further packets from the violating MAC addresses to maintain network security.
C, D
Explanation:
When a MAC limiting violation occurs on a Juniper switch, the switch will perform the following actions by default:
Step-by-Step Breakdown:
Port Disabled:
When the number of MAC addresses on an interface exceeds the configured limit, the port is automatically disabled to prevent further violations. This is a protective mechanism to prevent MAC address flooding.
Packet Dropped:
Additionally, packets from the violating MAC address are dropped to prevent any further communication from that address. This ensures that only valid MAC addresses are allowed to communicate through the interface.
Example Configuration:
set ethernet-switching-options secure-access-port interface <interface-name> mac-limit 5
If more than five MAC addresses are learned, the port is disabled, and excess packets are dropped.
Juniper
Reference: MAC Limiting: When the switch detects a MAC limiting violation, it disables the port and drops further packets from the violating MAC addresses to maintain network security.
Question #23
Why is EVPN often used in conjunction with VXLAN in modern data centers?
- A . To enable direct Internet access for applications.
- B . For providing Layer 2 connectivity over a Layer 3 fabric.
- C . To increase the physical bandwidth of the underlying network.
- D . To physically separate different customer environments.
Correct Answer: B
Question #24
Which operation mode command will display the mapping between the VLAN ID and ports on a switch?
- A . show route
- B . show ethernet-switching table
- C . show interfaces terse
- D . show vlans
Correct Answer: D
D
Explanation:
To display the mapping between VLAN IDs and ports on a Juniper switch, the show vlans command is
used.
Step-by-Step Breakdown:
VLAN Information:
The show vlans command displays detailed information about VLAN configurations, including the VLAN ID, associated interfaces (ports), and VLAN membership.
Command Example:
show vlans
This command will provide an output listing each VLAN, its ID, and the interfaces associated with the VLAN, enabling network engineers to quickly verify VLAN to port mappings.
Juniper
Reference: VLAN Verification: Use the show vlans command to verify which VLANs are configured on the switch and the ports that are members of those VLANs.
D
Explanation:
To display the mapping between VLAN IDs and ports on a Juniper switch, the show vlans command is
used.
Step-by-Step Breakdown:
VLAN Information:
The show vlans command displays detailed information about VLAN configurations, including the VLAN ID, associated interfaces (ports), and VLAN membership.
Command Example:
show vlans
This command will provide an output listing each VLAN, its ID, and the interfaces associated with the VLAN, enabling network engineers to quickly verify VLAN to port mappings.
Juniper
Reference: VLAN Verification: Use the show vlans command to verify which VLANs are configured on the switch and the ports that are members of those VLANs.
Question #25
Which of the following are true regarding port modes in a VLAN setup? (Choose two)
- A . An access port can carry traffic for multiple VLANs.
- B . A trunk port can carry traffic for multiple VLANs.
- C . An access port carries traffic only for a single VLAN.
- D . A trunk port is used exclusively for inter-switch links.
Correct Answer: BC
Question #26
What is the default route preference for a static route on a Junos device?
- A . 130
- B . 15
- C . 10
- D . 5
Correct Answer: D
Question #27
In Junos, which command is used to display the status of all interfaces?
- A . show interfaces terse
- B . show vlan brief
- C . show interfaces descriptions
- D . show ethernet-switching table
Correct Answer: A
Question #28
Which of the following are correct about OSPF router ID selection? (Choose two)
- A . It can be manually configured.
- B . It is chosen based on the highest IP address of any active interface by default.
- C . It is always the IP address of the loopback interface.
- D . It is selected based on the lowest MAC address.
Correct Answer: AB
Question #29
What is the function of the ‘Weight’ attribute in BGP, and where is it used in the route selection process?
- A . It is used to prioritize routes received from different EBGP peers and is considered before the AS_PATH attribute.
- B . It determines the stability of a route and is checked after the Local Preference attribute.
- C . It is a Cisco-specific attribute used to prefer paths from one BGP speaker over another, evaluated before the Local Preference.
- D . It is used to balance load among multiple links and is considered after the MED attribute.
Correct Answer: C
Question #30
Which statement is correct about the BGP AS path when advertising routes?
- A . The order of the AS path is not significant.
- B . The local AS number is added to the end of the AS path.
- C . The order of the AS path is only significant in IBGP.
- D . The local AS number is added to the beginning of the AS path.
Correct Answer: D
D
Explanation:
The BGP AS (Autonomous System) path attribute is crucial in path selection and loop prevention.
Each BGP router appends its local AS number to the beginning of the AS path when it advertises a route to an external BGP (eBGP) peer.
Step-by-Step Breakdown:
AS Path Attribute:
The AS path is a sequence of AS numbers that a route has traversed to reach a destination. Each AS adds its number to the front of the path, allowing BGP to track the route’s history.
Why the Local AS is Added at the Beginning:
When advertising a route to an eBGP neighbor, a BGP router adds its own AS number to the beginning of the AS path. This ensures that the AS path reflects the route’s journey accurately from the origin to the destination, and prevents loops in BGP. If the route returns to the same AS, the router will detect its AS number in the path and reject the route, preventing routing loops. Order of the AS Path:
The order is significant because BGP uses it to select the best path. A shorter AS path is preferred, as it indicates fewer hops between the source and destination. Juniper
Reference: AS Path Attribute: Junos devices append the local AS at the start of the AS path before advertising the route to an external peer.
D
Explanation:
The BGP AS (Autonomous System) path attribute is crucial in path selection and loop prevention.
Each BGP router appends its local AS number to the beginning of the AS path when it advertises a route to an external BGP (eBGP) peer.
Step-by-Step Breakdown:
AS Path Attribute:
The AS path is a sequence of AS numbers that a route has traversed to reach a destination. Each AS adds its number to the front of the path, allowing BGP to track the route’s history.
Why the Local AS is Added at the Beginning:
When advertising a route to an eBGP neighbor, a BGP router adds its own AS number to the beginning of the AS path. This ensures that the AS path reflects the route’s journey accurately from the origin to the destination, and prevents loops in BGP. If the route returns to the same AS, the router will detect its AS number in the path and reject the route, preventing routing loops. Order of the AS Path:
The order is significant because BGP uses it to select the best path. A shorter AS path is preferred, as it indicates fewer hops between the source and destination. Juniper
Reference: AS Path Attribute: Junos devices append the local AS at the start of the AS path before advertising the route to an external peer.