Juniper Juniper Certifications JN0-351 Questions & Answers

• Question 121:

  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.

  Correct Answer: BC

  Option B suggests that the BGP session is not established. This is correct because in the output, the state of the BGP session is shown as "Idle". In BGP, an "Idle" state means that the BGP session is not currently established1.

  Option C suggests that R1 is configured for AS 65400. This is also correct because in the output, it's shown that the local AS number is 654001. The local AS number represents the Autonomous System (AS) number of the router on which

  you're checking the BGP session1.

• Question 122:

  What is the default keepalive time for BGP?

  A. 10 seconds

  B. 60 seconds

  C. 30 seconds

  D. 90 seconds

  Correct Answer: B

  Explanation: The default keepalive time for BGP is 60 seconds1. The keepalive time is the interval at which BGP sends keepalive messages to maintain the connection with its peer1. If the keepalive message is not received within the hold time, the connection is considered lost1. By default, the hold time is three times the keepalive time, which is 180 seconds1.

• Question 123:

  Exhibit.

  

  You have configured the four EX Series switches with RSTP, as shown in the exhibit. You discover that whenever a link between switches goes up or down, the switches take longer than expected for RSTP to converge, using the default settings.

  In this scenario, which action would solve the delay in RSTP convergence?

  A. The hello-time must be increased.

  B. The force-version must be removed.

  C. The bridge priority for EX-4 must be set at 4000.

  D. The max-age must be increased to 20

  Correct Answer: B

  The exhibit shows the configuration of RSTP on EX-4, which has the command force-version stp. This command forces the switch to use the legacy STP protocol instead of RSTP, even though the switch supports RSTP1. This means that

  EX-4 will not be able to take advantage of the faster convergence and enhanced features of RSTP, such as edge ports, link type, and proposal/agreement sequence2.

  The other switches in the network are likely to be running RSTP, as it is the default protocol for EX Series switches3. Therefore, there will be a compatibility issue between EX-4 and the other switches, which will result in longer convergence

  times and suboptimal performance. The switch will also generate a warning message that says "Warning: STP version mismatch with neighbor" when it receives a BPDU from a RSTP neighbor1.

  To solve this problem, the force-version command must be removed from EX-4, so that it can run RSTP natively and interoperate with the other switches in the network. This will enable faster convergence and better stability for the network

  topology. To remove the command, you can use the delete protocols rstp force- version command in configuration mode1.

• Question 124:

  Which statement is correct about the IS-IS ISO NET address?

  A. An ISO NET address defined with a system ID of 0000.0000.0000 must be selected as the DIS.

  B. An ISO NET address must be unique for each device in the network.

  C. You can only define a single ISO NET address per device.

  D. The Area ID must match on all devices within a L2 area.

  Correct Answer: B

  An ISO NET address is a type of network address used by the IS-IS routing protocol. It identifies a point of connection to the network, such as a router interface, and is also called a Network Service Access Point (NSAP)1. An ISO NET address consists of three parts: an area ID, a system ID, and a selector2. The area ID identifies the IS-IS area to which the device belongs. The system ID uniquely identifies the device within the area. The selector identifies a specific service or function on the device, such as routing or management2. An ISO NET address must be unique for each device in the network, because it is used by IS-IS to establish adjacencies, exchange routing information, and compute shortest paths2. If two devices have the same ISO NET address, they will not be able to communicate with each other or with other devices in the network. Therefore, it is important to assign different ISO NET addresses to each device in the network.

• Question 125:

  You are receiving multiple BGP routes from an upstream neighbor and only want to advertise a single summarized prefix to your internal OSPF neighbors. This route should only be advertised when you are receiving these BGP routes from this neighbor.

  In this scenario, which type of route should you create?

  A. aggregate route

  B. static route using the resolve feature

  C. generate route

  D. static route using qualified next hops

  Correct Answer: A

  Explanation: In this scenario, you should create an aggregate route1. Aggregate routes are used for advertising summarized network prefixes1. They help minimize the number of routing tables in an IP network by consolidating selected

  multiple routes into a single route advertisement1. This approach is in contrast to non-aggregation routing, in which every routing table contains a unique entry for each route1. Therefore, option A is correct. Options B, C, and D are not correct

  because:

  Static route using the resolve feature: This type of route uses the resolve feature to install a static route in the routing table only if a specific condition is met1. However, it does not provide the capability to summarize multiple routes into a

  single prefix.

  Generate route: This type of route generates a route that is always present in the routing table and can be used to summarize routes. However, it does not have the capability to only advertise the route when specific BGP routes are being

  received from a neighbor1.

  Static route using qualified next hops: This type of route allows for the specification of multiple next-hop addresses for a static route1. However, it does not provide the capability to summarize multiple routes into a single prefix.

• Question 126:

  You want to ensure traffic is routed through a GRE tunnel.

  In this scenario, which two statements will satisfy this requirement? (Choose two.)

  A. Tunnel endpoints must have a route that directs traffic into the tunnel.

  B. All intermediary devices must have a route to the tunnel endpoints.

  C. Keepalives must be used on stateless tunneling protocols.

  D. BFD must be used on the stateless tunneling protocols.

  Correct Answer: AB

  Explanation: Option A is correct. For traffic to be sent through a GRE tunnel, there must be a route that directs the traffic into the tunnel. This is typically accomplished through the use of a static route or a dynamic routing protocol.

  Option B is correct. All intermediary devices must have a route to the tunnel endpoints34. In real-world scenarios, the tunnel endpoints for a tunnel going over the Internet must have globally reachable internet addresses. Otherwise, intermediate routers in the Internet cannot forward the tunneled packets.

• Question 127:

  Which two BGP attributes must be supported by all BGP implementations and must be included in every update? (Choose two.)

  A. AS path

  B. MED

  C. next hop

  D. community

  Correct Answer: AC

  Explanation: BGP attributes are properties that BGP uses for route advertisement, path selection, and loop prevention1. There are four categories of BGP attributes123:

  Well-known mandatory: Must be recognized by all BGP routers, present in all BGP updates, and passed on to other BGP routers123.

  Well-known discretionary: Supported by all BGP implementations, and are optionally included in BGP updates1.

  Optional transitive: May not be supported by all implementations of BGP1. Optional non-transitive: May not be supported by all implementations of BGP1. The well-known mandatory attributes must be supported by all BGP implementations

  and must be included in every update123. These include the AS path and next hop attributes23. Therefore, options A and C are correct.

• Question 128:

  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

  Correct Answer: B

  The management IP address of a device is the IP address that is used to access the device for configuration and monitoring purposes. It is usually assigned to a dedicatedmanagement interface that is separate from the data interfaces. The

  management interface can be accessed via SSH, Telnet, HTTP, or other protocols. In the exhibit, the list of interfaces and their statuses shows that the management interface isme0. This interface has an admin status ofup, a protocol status

  ofinet, a local address of172.23.12.100/24, and a remote address ofunspecified. This means that the me0 interface is active, has an IPv4 address assigned, and is not connected to another device. Therefore, the management IP address of

  the device shown in the exhibit is172.23.12.100.

  References:

  [Management Interfaces Overview] : [Displaying Interface Status Information]

• Question 129:

  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.

  Correct Answer: 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.

  References:

  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 130:

  Which two statements about redundant trunk groups on EX Series switches are correct? (Choose two.)

  A. Redundant trunk groups load-balance traffic across two designated uplink interfaces.

  B. If the active link fails, then the secondary link automatically takes over.

  C. Layer 2 control traffic is permitted on the secondary link

  D. Redundant trunk groups must be connected to the same aggregation switch.

  Correct Answer: BD

  Explanation: Redundant Trunk Groups (RTGs) on EX Series switches provide a simple solution for network recovery when a trunk port on a switch goes down1. They are configured on the access switch and contain two links: a primary or

  active link, and a secondary link1. Therefore, option B is correct because if the active link fails, the secondary link automatically starts forwarding data traffic without waiting for normal spanning-tree protocol convergence1.

  Option D is also correct. In a typical enterprise network composed of distribution and access layers, RTGs are used where one Access switch is connected to two different uplink switches2. This implies that RTGs must be connected to the

  same aggregation switch2.