Juniper Juniper Certifications JN0-351 Questions & Answers

• Question 111:

  You are attempting to configure the initial two aggregated Ethernet interfaces on a router but there are no aggregated Ethernet interfaces available. In this scenario, which configuration will enable these interfaces on this router?

  

  A. B. C. D.

  A. Option A

  B. Option B

  C. Option C

  D. Option D

  Correct Answer: C

  Explanation: The correct answer to your question is C. Option C. Here is why:

  Option C shows the configuration of the chassis statement, which defines the properties of the router chassis, such as the number of aggregated Ethernet interfaces, the number of FPCs, and the number of PICs1. To enable aggregated

  Ethernet interfaces on a router, you need to specify the aggregated-devices statement under the chassis statement and set the ethernet parameter to the desired number of interfaces2. For example, to enable two aggregated Ethernet

  interfaces, you can use the following configuration:

  chassis { aggregated-devices { ethernet { device-count 2; } } } Option C shows this configuration with the device-count set to 2, which will enable two aggregated Ethernet interfaces on the router. The other options do not show this

  configuration and will not enable any aggregated Ethernet interfaces on the router.

  Therefore, option C is the correct answer to your question.

• Question 112:

  Exhibit.

  

  Which router will become the OSPF BDR if all routers are powered on at the same time?

  A. R4

  B. R1

  C. R3

  D. R2

  Correct Answer: A

  OSPF DR/BDR election is a process that occurs on multi-access data links. It is intended to select two OSPF nodes: one to be acting as the Designated Router (DR), and another to be acting as the Backup Designated Router (BDR).The DR and BDR are responsible for generating network LSAs for the multi-access network and synchronizing the LSDB with other routers on the same network1. The DR/BDR election is based on two criteria: the OSPF priority and the router ID. The OSPF priority is a value between 0 and 255 that can be configured on each interface participating in OSPF. The default priority is 1. A priority of 0 means that the router will not participate in the election and will never become a DR or BDR. The router with the highest priority will become the DR, and the router with the second highest priority will become the BDR. If there is a tie in priority, then

  the router ID is used as a tie-breaker. The router ID is a 32-bit number that uniquely identifies each router in an OSPF domain.It can be manually configured or automatically derived from the highest IP address on a loopback interface or any

  active interface2.

  In this scenario, all routers have the same priority of 1, so the router ID will determine the outcome of the election. The router IDs are shown in the exhibit as RID values. The highest RID belongs to R4 (10.10.10.4), so R4 will become the DR.

  The second highest RID belongs to R3 (10.10.10.3), so R3 will become the BDR.

  References:

  1:OSPF DR/BDR Election: Process, Configuration, and Tuning2:OSPF Designated Router (DR) and Backup Designated Router (BDR)

• Question 113:

  You have two OSPF routers forming an adjacency. R1 has a priority of 32 and a router ID of 192.168.1.2. R2 has a priority of 64 and a router ID of 192.168.1.1. The routers were started at the same time and all other OSPF settings are the default settings.

  Which statement is correct in this scenario?

  A. At least three routers are required for a DR/BDR election

  B. Router IDs must match for an adjacency to form.

  C. R2 will be the BDR.

  D. R1 will be the BDR.

  Correct Answer: D

  Explanation: In OSPF, the Designated Router (DR) and Backup Designated Router (BDR) are elected based on the priority of the routers1. The router with the highest priority becomes the DR, and the router with the second highest priority becomes the BDR1. If there is a tie in priority, then the router with the highest Router ID is chosen1. In this scenario, R2 has a higher priority (64) than R1 (32), so R2 will become the DR1. Since R1 has the second highest priority, it will become the BDR1. Therefore, option D is correct.

• Question 114:

  Exhibit

  

  Your ISP is announcing a default route to both R1 and R2. You want your network routers to forward all Internet traffic through the R1 device Which BGP attribute would you use?

  A. MED

  B. next-hop

  C. local preference

  D. origin

  Correct Answer: C

  Explanation: The BGP attribute that you would use to forward all Internet traffic through the R1 device is the local preference1.

  The local preference is an attribute that is used within an autonomous system (AS) and exchanged between iBGP routers1. It is used to select an exit point from the AS1. The path with the highest local preference is preferred1. By setting a

  higher local preference for the routes received from R1, you can make R1 the preferred exit point for all Internet traffic1.

• Question 115:

  Exhibit.

  

  You want to enable redundancy for the EBGP peering between the two routers shown in the exhibit. Which three actions will you perform in this scenario? (Choose three.)

  A. Configure BGP multihop.

  B. Configure loopback interface peering.

  C. Configure routes for the peer loopback interface IP addresses.

  D. Configure an MD5 peer authentication.

  E. Configure a cluster ID.

  Correct Answer: ABC

  A is correct because you need to configure BGP multihop to enable redundancy for the EBGP peering between the two routers. BGP multihop is a feature that allows BGP peers to establish a session over multiple hops, instead of requiring them to be directly connected1. By default, EBGP peers use a time-to-live (TTL) value of 1 for their packets, which means that they can only reach adjacent neighbors1. However, if you configure BGP multihop with a higher TTL value, you can allow EBGP peers to communicate over multiple routers in between1. This can provide redundancy in case of a link failure or a router failure between the EBGP peers. B is correct because you need to configure loopback interface peering to enable redundancy for the EBGP peering between the two routers. Loopback interface peering is a technique that uses loopback interfaces as the source and destination addresses for BGP sessions, instead of physical interfaces2. Loopback interfaces are virtual interfaces that are always up andreachable as long as the router is operational2. By using loopback interface peering, you can avoid the dependency on a single physical interface or link for the BGP session, and use multiple paths to reach the loopback address of the peer2. This can provide redundancy and load balancing for the EBGP peering. C is correct because you need to configure routes for the peer loopback interface IP addresses to enable redundancy for the EBGP peering between the two routers. Routes for the peer loopback interface IP addresses are necessary to ensure that the routers can reach each other's loopback addresses over multiple hops2. You can use static routes or dynamic routing protocols to advertise and learn the routes for the peer loopback interface IP addresses2. Without these routes, the routers will not be able to establish or maintain the BGP session using their loopback interfaces.

• Question 116:

  Exhibit.

  

  The ispi _ inet. 0 route table has currently no routes in it.

  What will happen when you commit the configuration shown on the exhibit?

  A. The inet. 0 route table will be completely overwritten by the ispi . inet. 0 route table.

  B. The inet. 0 route table will be imported into the ispi . inet. 0 route table.

  C. The ISPI . inet. 0 route table will be completely overwritten by the inet. o route table.

  D. The ISPI . inet. 0 route table will be imported into the inet. 0 route table.

  Correct Answer: B

  Explanation: The configuration shown in the exhibit is an example of a routing instance of type virtual-router. A routing instance is a collection of routing tables, interfaces, and routing protocol parameters that create a separate routing domain

  on a Juniper device1. A virtual-router routing instance allows administrators to divide a device into multiple independent virtual routers, each with its own routing table2. The configuration also includes a rib-group statement, which is used to

  import routes from one routing table to another. A rib-group consists of an import-rib statement, which specifies the source routing table, and an export-rib statement, which specifies the destination routing table.

  In this case, the rib-group name is inet-to-ispi, and the import-rib statement specifies inet.0 as the source routing table. The export-rib statement specifies ispi.inet.0 as the destination routing table. This means that the routes from inet.0 will be

  imported into ispi.inet.0. Therefore, the correct answer is B. The inet.0 route table will be imported into the ispi.inet.0 route table.

  References:

  1: Routing Instances Overview 2: Virtual Routing Instances : [rib-group (Routing Options)]

• Question 117:

  Exhibit

  

  Your BGP neighbors, one in the USA and one in France, are not establishing a connection with each other. Referring to the exhibit, which statement is correct?

  A. The BFD liveness is set too low.

  B. The BFD liveness must be configured on the BGP neighbor.

  C. The BFD liveness must be configured on the BGP group.

  D. The BFD liveness is set too high.

  Correct Answer: B

  The exhibit shows the configuration of BFD liveness detection for BGP at the global level, which applies to all BGP neighbors by default1. However, this configuration does not specify the session mode, which determines whether BFD uses

  single-hop or multihop mode to communicate with a neighbor2. For single-hop BGP neighbors, which are directly connected on the same subnet, the session mode can be either automatic or single-hop. For multihop BGPneighbors, which are

  not directly connected and require multiple hops to reach, the session mode must be multihop2.

  Since your BGP neighbors are in different countries, they are likely to be multihop neighbors. Therefore, you need to configure the session mode as multihop for each neighbor individually at the [edit protocols bgp group group-name neighbor

  address bfd-liveness-detection] hierarchy level2. For example:

  protocols { bgp { group usa { neighbor 192.0.2.1 { bfd-liveness-detection { session-mode multihop; } } } group france { neighbor 198.51.100.1 { bfd-liveness-detection { session-mode multihop; } } } } }

  If you do not configure the session mode for multihop neighbors, BFD will use the default mode of automatic, which will try to use single-hop mode and fail to establish a BFD session with the remote neighbor2. This will prevent BGP from

  using BFD to detect liveliness and failover.

  Therefore, the answer B is correct, as you need to configure the BFD liveness detection on the BGP neighbor level with the appropriate session mode for multihop neighbors.

• Question 118:

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

  A. Redundant trunk groups use spanning tree to provide loop-free redundant uplinks.

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

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

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

  Correct Answer: CD

  C is correct because Layer 2 control traffic is permitted on the secondary link of a redundant trunk group (RTG) on EX Series switches. Layer 2 control traffic includes protocols such as LLDP, LACP, and STP, which are used to exchange information and coordinate actions between switches1. According to the Juniper Networks documentation2, Layer 2 control traffic is allowed to pass through both the active and the secondary links of an RTG, but data traffic is only forwarded through the active link. This allows the switches to maintain their Layer 2 adjacencies and monitor the link status on both links. D is correct because if the active link fails, then the secondary link automatically takes over in an RTG on EX Series switches. An RTG consists of two trunk links: an active or primary link, and a secondary or backup link2. The active link is used to forward data traffic, while the secondary link is in standby mode. If the active link fails or becomes unavailable, the secondary link immediately transitions to a forwarding state and takes over the data traffic without waiting for normal STP convergence2. This provides fast recovery and redundancy for the network.

• Question 119:

  Exhibit

  

  Which command displays the output shown in the exhibit?

  A. show route forwarding-table

  B. show ethernet-switching table

  C. show ethernet--switching table extensive

  D. show route forwarding--table family ethernet-switching

  Correct Answer: B

  The output shown in the exhibit is a brief display of the Ethernet switching table, which shows the learned Layer 2 MAC addresses for each VLAN and interface1. The command show ethernet-switching table displays the Ethernet switching table with brief information, such as the destination MAC address, the VLAN name, the forwarding state, and the interface name1. The command show route forwarding-table displays the routing table information for each protocol family, such as inet, inet6, mpls, iso, and so on2. It does not show the Ethernet switching table or the MAC addresses. The command show ethernet-switching table extensive displays the Ethernet switching table with extensive information, such as the destination MAC address, the VLAN name, the forwarding state, the interface name, the VLAN index, and the tag type1. It shows more details than the brief output shown in the exhibit. The command show route forwarding-table family ethernet-switching displays the routing table information for the ethernet-switching protocol family, whichshows the destination MAC address, the next-hop MAC address, and the interface name3. It does not show the VLAN name or the forwarding state.

• Question 120:

  You want to use filter-based forwarding (FBF) on your Internet peering router to load- balance traffic to two directly connected ISPs based on the source address.

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

  A. FBF uses the no-forwarding routing instance type.

  B. FBF uses the forwarding routing instance type.

  C. RIB groups are used to copy routes from the inet. o routing table.

  D. RIB groups are used to hide routes in the inet. 0 routing table.

  Correct Answer: BC

  Option B is correct. Filter-based forwarding (FBF), also known as Policy Based Routing (PBR), uses the forwarding routing instance type12. Option C is correct. Routing Information Base (RIB) groups are used to copy routes from one routing table to another34. In the context of FBF, RIB groups can be used to copy routes from the inet.0 routing table34. Option A is incorrect. FBF does not use the no-forwarding routing instance type15. Option D is incorrect. RIB groups are not used to hide routes in the inet.0 routing table34. They are used to share or copy routes between different routing tables34.