Free Juniper JN0-351 Practice Exams

Question #1

What is the maximum allowable MTU size for a default GRE tunnel without IPv4 traffic fragmentation?

A . 1496 bytes
B . 1480 bytes
C . 1500 bytes
D . 1476 bytes

Question #2

Exhibit

You are a network operator troubleshooting BGP connectivity.

Which two statements are correct about the output shown in the exhibit? (Choose two.)

A . Peer 10.32.1.2 is configured for AS 63645.
B . The BGP session is not established.
C . The R1 is configured for AS 65400.
D . The routers are exchanging IPv4 routes.

Reveal Solution Hide Solution

Question #3

What is the default keepalive time for BGP?

A . 10 seconds
B . 60 seconds
C . 30 seconds
D . 90 seconds

Reveal Solution Hide Solution

Question #4

Which two statements are correct about tunnels? (Choose two.)

A . BFD cannot be used to monitor tunnels.
B . Tunnel endpoints must have a valid route to the remote tunnel endpoint.
C . IP-IP tunnels are stateful.
D . Tunnels add additional overhead to packet size.

Reveal Solution Hide Solution

Correct Answer: BD
BD

Explanation:

A tunnel is a connection between two computer networks, in which data is sent from one network to another through an encrypted link. Tunnels are commonly used to secure data communications between two networks or to connect two networks that use different protocols.

Option B is correct, because tunnel endpoints must have a valid route to the remote tunnel endpoint. A tunnel endpoint is the device that initiates or terminates a tunnel connection. For a tunnel to be established, both endpoints must be able to reach each other over the underlying network. This means that they must have a valid route to the IP address of the remote endpoint1.

Option D is correct, because tunnels add additional overhead to packet size. Tunnels work by encapsulating packets: wrapping packets inside of other packets. This means that the original packet becomes the payload of the surrounding packet, and the surrounding packet has its own header and trailer. The header and trailer of the surrounding packet add extra bytes to the packet size, which is called overhead. Overhead can reduce the efficiency and performance of a network, as it consumes more bandwidth and processing power2.

Option A is incorrect, because BFD can be used to monitor tunnels. BFD is a protocol that can be used to quickly detect failures in the forwarding path between two adjacent routers or switches. BFD can be integrated with various routing protocols and link aggregation protocols to provide faster convergence and fault recovery. BFD can also be used to monitor the connectivity of tunnels, such as GRE, IPsec, or MPLS.

Option C is incorrect, because IP-IP tunnels are stateless. IP-IP tunnels are a type of tunnels that use IP as both the encapsulating and encapsulated protocol. IP-IP tunnels are simple and easy to configure, but they do not provide any security or authentication features. IP-IP tunnels are stateless, which means that they do not keep track of the state or status of the tunnel connection. Stateless tunnels do not require any signaling or negotiation between the endpoints, but they also do not provide any error detection or recovery mechanisms.

Reference: 1: What is Tunneling? | Tunneling in Networking 2: What Is Tunnel In Networking, Its Types, And Its

Benefits? : [Configuring Bidirectional Forwarding Detection] : [IP-IP Tunneling]

Question #5

You are configuring an IS-IS IGP network and do not see the IS-IS adjacencies established. In this scenario, what are two reasons for this problem? (Choose two.)

A . MTU is not at least 1492 bytes.
B . IP subnets are not a /30 address.
C . The Level 2 routers have mismatched areas.
D . The lo0 interface is not included as an IS-IS interface.

Reveal Solution Hide Solution

Question #6

Which statement is correct about graceful Routing Engine switchover (GRES)?

A . The PFE restarts and the kernel and interface information is lost.
B . GRES has a helper mode and a restarting mode.
C . When combined with NSR, routing is preserved and the new master RE does not restart rpd.
D . With no other high availability features enabled, routing is preserved and the new master RE does not restart rpd.

Reveal Solution Hide Solution

Question #7

Exhibit.

What is the management IP address of the device shown in the exhibit?

A . 10.210.20.233
B . 172.23.12.100
C . 128.0.0.1
D . 172.23.11.10

Reveal Solution Hide Solution

Question #8

You are a network operator who wants to add a second ISP connection and remove the default route to the existing ISP You decide to deploy the BGP protocol in the network.

What two statements are correct in this scenario? (Choose two.)

A . IBGP updates the next-hop attribute to ensure reachability within an AS.
B . IBGP peers advertise routes received from EBGP peers to other IBGP peers.
C . IBGP peers advertise routes received from IBGP peers to other IBGP peers.
D . EBGP peers advertise routes received from IBGP peers to other EBGP peers.

Reveal Solution Hide Solution

Question #9

Exhibit

You have configured a GRE tunnel. To reduce the risk of dropping traffic, you have configured a keepalive OAM probe to monitor the state of the tunnel; however, traffic drops are still occurring.

Referring to the exhibit, what is the problem?

A . For GRE tunnels, the OAM protocol requires that the BFD protocols also be used.
B . The "event link-adjacency-loss" option must be set.
C . LLDP needs to be removed from the gr-1/1/10.1 interface.
D . The hold-time value must be two times the keepalive-time value

Reveal Solution Hide Solution

Correct Answer: D
D

Explanation:

A keepalive OAM probe is a mechanism that can be used to monitor the state of a GRE tunnel and detect any failures in the tunnel path. A keepalive OAM probe consists of sending periodic packets from one end of the tunnel to the other and expecting a reply. If no reply is received within a specified time, the tunnel is considered down and the line protocol of the tunnel interface is changed to down1.

To configure a keepalive OAM probe for a GRE tunnel, you need to specify two parameters: the keepalive-time and the hold-time. The keepalive-time is the interval between each keepalive packet sent by the local router. The hold-time is the maximum time that the local router waits for a reply from the remote router before declaring the tunnel down2.

According to the Juniper Networks documentation, the hold-time value must be two times the keepalive-time value for a GRE tunnel2. This is because the hold-time value must account for both the round-trip time of the keepalive packet and the processing time of the remote router. If the hold-time value is too small, it may cause false positives and unnecessary tunnel flaps.

In the exhibit, the configuration shows that the keepalive-time is set to 10 seconds and the hold-time

is set to 15 seconds for the gr-1/1/10.1 interface. This means that the local router will send a keepalive packet every 10 seconds and will wait for 15 seconds for a reply from the remote router. However, this hold-time value is not two times the keepalive-time value, which violates the recommended configuration. This may cause traffic drops if the remote router takes longer than 15 seconds to reply.

Therefore, option D is correct, because the hold-time value must be two times the keepalive-time value for a GRE tunnel. Option A is incorrect, because BFD is not required for GRE tunnels; BFD is another protocol that can be used to monitor tunnels, but it is not compatible with GRE keepalives3. Option B is incorrect, because the “event link-adjacency-loss” option is not related to GRE tunnels; it is an option that can be used to trigger an action when a link goes down4. Option C is incorrect, because LLDP does not need to be removed from the gr-1/1/10.1 interface; LLDP is a protocol that can be used to discover neighboring devices and their capabilities, but it does not interfere with GRE tunnels5.

Reference:

1: Configuring Keepalive Time and Hold time for a GRE Tunnel Interface 2: keepalive | Junos OS |

Juniper Networks 3: Configuring Bidirectional Forwarding Detection 4: event link-adjacency-loss |

Junos OS | Juniper Networks 5: Understanding Link Layer Discovery Protocol