Juniper JN0-280 Online Practice Questions and Exam Preparation

Juniper JN0-280 Online Questions & Answers

• Question 111:

  MACsec provides protection against which two types of threats? (Choose two.)

  A. Data decryption
  B. Playback attacks
  C. Hashing attacks
  D. Man-in-the-middle attack
  B. Playback attacks
  D. Man-in-the-middle attack

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  Explanation/Reference:

  MACsec (Media Access Control Security)provides data confidentiality, integrity, and origin authenticity at Layer 2, protecting against several types of threats.

  Step-by-Step Breakdown:

  Man-in-the-Middle Attack Protection:MACsec encrypts traffic at Layer 2, preventingman-in-the- middle attacks where an attacker intercepts and manipulates traffic between two communicating devices. Since the data is encrypted, any

  intercepted packets are unreadable.

  Protection Against Playback Attacks:MACsec also protects against playback attacks by using sequence numbers and timestamps to ensure that old, replayed packets are not accepted by the receiver.

  Juniper Reference:

  MACsec Configuration: Juniper devices support MACsec for securing Layer 2 communications, ensuring protection against replay and man-in-the-middle attacks in sensitive environments.

• Question 112:

  Which of the following BGP attributes is considered first in the route selection process?

  A. Local Preference
  B. AS Path Length
  C. Origin
  D. MED
  A. Local Preference

• Question 113:

  Which two statements describe an OSPF ABR? (Choose two.)

  A. By default, an ABR does not need to have any links in the backbone area.
  B. By default, an ABR is an OSPF router with links in two areas.
  C. By default, an ABR is an OSPF router with all of its links in one area.
  D. By default, an ABR must have one link in the OSPF backbone area.
  A. By default, an ABR does not need to have any links in the backbone area.
  B. By default, an ABR is an OSPF router with links in two areas.
  D. By default, an ABR must have one link in the OSPF backbone area.

• Question 114:

  You are troubleshooting a downed BGP session.

  

  Referring to the exhibit, what is the cause of the problem?

  A. The UDP session between the peers has not been established.
  B. The local peer has sent an Open message but not received one from the remote peer.
  C. The TCP session between the peers has not been established.
  D. The local peer has sent an Update message but not received one from the remote peer.
  C. The TCP session between the peers has not been established.

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  Explanation/Reference:

  The BGP session in the exhibit shows the state as Connect , which indicates that the TCP session between the BGP peers has not been fully established.

  Step-by-Step Breakdown:

  BGP State "Connect":

  The Connect state is the second stage in the BGP finite state machine (FSM). At this stage, BGP is trying to establish a TCP session with the peer, but the session has not yet been successfully established. A successful TCP three-way

  handshake (SYN, SYN-ACK, ACK) is required before BGP can progress to the OpenSent state, where the peers exchange BGP Open messages.

  Possible Causes:

  A firewall blocking TCP port 179 .

  Incorrect IP addresses or network connectivity issues between the BGP peers.

  Juniper Reference:

  BGP Troubleshooting: In Junos, if a BGP session is stuck in the Connect state, the issue is likely due to a failure in establishing the underlying TCP connection.

• Question 115:

  Exhibit:

  

  How many stages are shown in the exhibit?

  A. 2
  B. 5
  C. 6
  D. 3
  D. 3

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  Explanation/Reference:

  The exhibit shows a Folded IP Clos Architecture , which is also referred to as a 3-stage Clos network design. This architecture typically consists of two layers of switches:

  Spine Layer: The top row of switches.

  Leaf Layer: The bottom row of switches.

  Step-by-Step Breakdown:

  Clos Architecture:A 3-stage Clos network has two types of devices: spine and leaf. In this design, each leaf switch connects to every spine switch, providing a high level of redundancy and load balancing.

  Stage

  Stage 1: The first set of leaf switches.

  Stage 2: The spine switches.

  Stage 3: The second set of leaf switches.

  The Folded Clos architecture shown here effectively "folds" the 3-stage design by combining the ingress and egress leaf layers into one, reducing it to two visible layers, but still maintaining the overall3-stage architecture .

  Juniper Reference:

  IP Clos Architecture: The 3-stage Clos design is commonly used in modern data centers for high availability, redundancy, and scalability.

• Question 116:

  Layer 2 interfaces operate in which two modes? (Choose two.)

  A. Access
  B. Modular
  C. Trunk
  D. Tagged
  A. Access
  C. Trunk

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  Explanation/Reference:

  Comprehensive Detailed Step by Step 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 portsare 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 portsare 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 117:

  Bidirectional Forwarding Detection (BFD) is primarily used for:

  A. Encrypting data packets
  B. Detecting slow links in the network
  C. Quick failure detection in forwarding paths
  D. Aggregating multiple links
  C. Quick failure detection in forwarding paths

• Question 118:

  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.
  A. It can be manually configured.
  B. It is chosen based on the highest IP address of any active interface by default.

• Question 119:

  In a Virtual Chassis configuration, which of the following is true?

  A. It allows physical stacking of switches that are geographically dispersed.
  B. It reduces the operational complexity of managing multiple switches.
  C. It decreases network redundancy and reliability.
  D. Only two switches can be connected in a Virtual Chassis setup.
  B. It reduces the operational complexity of managing multiple switches.

• Question 120:

  Referring to the exhibit,

  

  which next hop will be preferred in the routing table?

  A. Next hop IP address 172.25.20.254 will be preferred.
  B. Neither next hop will be preferred.
  C. Next hop IP address 172.25.20.200 will be preferred.
  D. Both next hops will be preferred.
  C. Next hop IP address 172.25.20.200 will be preferred.

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  Explanation/Reference:

  In the exhibit, we see a static route configuration with two possible next hops for the default route (0.0.0.0/0):

  next-hop 172.25.20.254with the default preference of 7.

  qualified-next-hop 172.25.20.200with a preference of 6.

  Step-by-Step Breakdown:

  Preference Value:In Junos OS, the preference value is used to determine which route should be preferred in the routing table. The lower the preference value, the higher the priority for the route.

  Comparison:In this case:

  The next hop 172.25.20.254 has a preference of . 7

  The qualified-next-hop 172.25.20.200 has a preference of . 6

  Preferred Next Hop:Since 172.25.20.200 has a lower preference (6) compared to 172.25.20.254 (7), it will be the preferred next hop in the routing table, assuming both next hops are reachable.

  Juniper Reference:

  Qualified Next Hop: In Junos, static routes with multiple next-hop options are selected based on the preference value , with the lower value being preferred.