Juniper JN0-280 Online Practice Questions and Exam Preparation

Juniper JN0-280 Online Questions & Answers

• Question 91:

  By default, which two statements are correct about BGP advertisements? (Choose two.)

  A. BGP peers advertise routes received from EBGP peers to other IBGP peers.
  B. BGP peers advertise routes received from IBGP peers to other IBGP peers.
  C. BGP peers advertise routes from EBGP peers to other IBGP peers using its own address as thenext hop.
  D. BGP peers advertise routes from IBGP peers to EBGP peers using its own address as the next hop.
  A. BGP peers advertise routes received from EBGP peers to other IBGP peers.
  D. BGP peers advertise routes from IBGP peers to EBGP peers using its own address as the next hop.

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  Explanation/Reference:

  BGP (Border Gateway Protocol)has specific rules for route advertisement between peers.

  Step-by-Step Breakdown:

  EBGP to IBGP Route Propagation:

  BGP peers advertise routes learned from EBGP peers IBGP peers to within the same AS. This ensures that routes learned from external networks are propagated internally within the AS.

  IBGP to EBGP Route Propagation:

  Routes learned from IBGP peers can be advertised to EBGP peers , but when advertising these routes, the router uses its own IP address as the next hop .

  IBGP Split Horizon:

  By default, IBGP peers do not advertise routes learned from one IBGP peer to another IBGP peer. This rule (IBGP split horizon) prevents routing loops within an AS.

  Juniper Reference:

  BGP Advertisement Rules: Junos adheres to BGP standards, where IBGP peers do not propagate routes to other IBGP peers, but EBGP peers receive IBGP routes with the advertising router as the next hop.

• Question 92:

  What is the main advantage of using MACsec?

  A. It increases the speed of the network.
  B. It provides Layer 2 encryption for data confidentiality and integrity.
  C. It creates multiple virtual networks over a single physical infrastructure.
  D. It allows for the use of longer cable runs.
  B. It provides Layer 2 encryption for data confidentiality and integrity.

• Question 93:

  When considering bidirectional forwarding detection, which two statements are correct? (Choose two.)

  A. The BFD default minimum interval is 3.
  B. You can configure BFD per interface within the protocol stanza.
  C. The BFD operation always consists of minimum intervals and multipliers.
  D. The BFD default multiplier is 5.
  B. You can configure BFD per interface within the protocol stanza.
  C. The BFD operation always consists of minimum intervals and multipliers.

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  Explanation/Reference:

  Bidirectional Forwarding Detection (BFD)is a protocol used to detect faults in the forwarding path between two routers. It provides rapid failure detection, enhancing the performance of routing protocols like OSPF, BGP, and IS-IS.

  Step-by-Step Breakdown:

  Per Interface Configuration:BFD can be configured on a per-interface basis within the protocol stanza (e.g., OSPF, BGP). This allows granular control over where BFD is enabled and the failure detection intervals for specific interfaces.

  Minimum Interval and Multiplier:BFD uses a minimum interval (the time between BFD control packets) and a multiplier (the number of missed packets before the path is declared down). The combination of these two defines the detection time

  for failures.

  Juniper Reference:

  BFD Configuration: In Juniper, BFD is configurable within routing protocol stanzas, with the failure detection mechanism always based on minimum intervals and multipliers.

• Question 94:

  When configuring static routes, which command is typically used?

  A. set protocols static route
  B. set route aggregate
  C. set firewall filter
  D. set routing-options rib-groups
  A. set protocols static route

• Question 95:

  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.
  D. The default next hop is reject.

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  Explanation/Reference:

  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 todiscard (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 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 96:

  Referring to the exhibit,

  

  at which interval will the interface be considered down if no hello packets are received?

  A. 2000 seconds
  B. 400 milliseconds
  C. 400 seconds
  D. 2000 milliseconds
  D. 2000 milliseconds

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  Explanation/Reference:

  The exhibit shows the configuration of Bidirectional Forwarding Detection (BFD) for OSPF on interface xe- 0/0/4.0, with the following parameters:

  minimum-interval: 400 milliseconds

  multiplier: 5

  Step-by-Step Breakdown:

  BFD Liveness Detection:BFD is used to detect link failures at sub-second intervals, providing faster convergence times for routing protocols like OSPF. The minimum-interval is the time between BFD control packets (in milliseconds), and the

  multiplier indicates how many missed BFD packets trigger a failure.

  Calculating Failure Detection Time:The failure detection interval is calculated as:

  In this case:

  Conclusion:If no BFD control packets are received within 2000 milliseconds (2 seconds) , the interface will be considered down, triggering OSPF to recalculate routes.

  Juniper Reference:

  BFD Configuration: BFD parameters such as minimum-interval and multiplier are used to fine-tune the failure detection time for faster convergence.

• Question 97:

  Which command on a router is used to view the current routing table?

  A. show routing-table
  B. show route
  C. display ip routing-table
  D. check route information
  B. show route

• Question 98:

  Which statement is correct about areas in OSPF?

  A. An OSPF area is used to segment Layer 2 broadcast domains.
  B. OSPF areas are used to isolate the effects of a broadcast storm.
  C. OSPF areas are used to reduce the size of the link-state database.
  D. An OSPF area is used to signify the autonomous system to which each device belongs.
  C. OSPF areas are used to reduce the size of the link-state database.

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  Explanation/Reference:

  In OSPF (Open Shortest Path First) , areas are used to segment a network into smaller, more manageable pieces to improve scalability. By dividing a network into areas, OSPF can reduce the size of thelink-state database (LSDB) , which

  helps routers process updates more efficiently.

  Step-by-Step Breakdown:

  Purpose of OSPF Areas:OSPF areas allow for hierarchical routing within the OSPF domain. Routers in the same area have identical LSDBs, but routers in different areas do not exchange full link-state information. Instead, they exchange

  summarized routes, which reduces the LSDB size and CPU /memory usage.

  Benefits:Reducing the LSDB size improves scalability and ensures faster convergence in larger networks. Area 0 is the backbone area, and all other areas must connect to it, forming a hierarchical structure.

  Juniper Reference:

  OSPF Configuration: Areas in OSPF are configured to optimize network performance by limiting the scope of link-state advertisements (LSAs) to within an area.

• Question 99:

  Which of the following is a key benefit of implementing High Availability (HA) in a network?

  A. Reduced network security
  B. Increased network downtime
  C. Enhanced data redundancy
  D. Slower data recovery
  C. Enhanced data redundancy

• Question 100:

  Referring to the exhibit, what is the route preference of the 172.25.11.254 next hop?

  

  A. 5
  B. 10
  C. 130
  D. 140
  A. 5

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  Explanation/Reference:

  In the exhibit, we see two next-hop addresses for the default static route (0.0.0.0/0):

  The first next hop is 172.25.11.254 , with no specified preference.

  The second next hop is 172.25.11.200 , with a specified preference of 140 .

  Step-by-Step Breakdown:

  Default Static Route Preference:If no preference is explicitly set for a next hop in Junos, it defaults to5 for static routes. Determining Preference:In this case, the next hop 172.25.11.254 does not have an explicit preference defined, so it will

  use the default value of . The second next hop has a preference of 5 140 , which is higher,meaning it will only be used if the primary next hop is unavailable.

  Juniper Reference:

  Static Route Preference: In Junos, the default preference for static routes is , and this value is applied 5 unless overridden by the preference parameter.