Real Juniper JN0-351 Exam Dumps with Correct 67 Questions and Answers [Q22-Q40]

Real Juniper JN0-351 Exam Dumps with Correct 67 Questions and Answers

Valid JN0-351 Test Answers & Juniper JN0-351 Exam PDF

NEW QUESTION # 22
Which two mechanisms are part of building and maintaining a Layer 2 bridge table? (Choose two.)

• A. listening
• B. blocking
• C. flooding
• D. learning

Answer: C,D

Explanation:
Option B is correct. Flooding is a mechanism used in Layer 2 bridging where the switch sends incoming packets to all its ports except for the port where the packet originated1. This is done when the switch doesn't know the destination MAC address or when the packet is a broadcast or multicast1.
Option C is correct. Learning is another mechanism used in Layer 2 bridging where the switch learns the source MAC addresses of incoming packets and associates them with the port on which they were received23. This information is stored in a MAC address table, also known as a bridge table23.
Option A is incorrect. Blocking is a state in Spanning Tree Protocol (STP) used to prevent loops in a network2. It's not a mechanism used in building and maintaining a Layer 2 bridge table2.
Option D is incorrect. Listening is also a state in Spanning Tree Protocol (STP) where the switch listens for BPDUs to make sure no loops occur in the network before transitioning to the learning state2. It's not a mechanism used in building and maintaining a Layer 2 bridge table2.

NEW QUESTION # 23
What are two characteristics of RSTP alternate ports? (Choose two.)

• A. RSTP alternate ports are active ports used to forward frames toward the root bridge.
• B. RSTP alternate ports provide an alternate higher cost path to the root bridge.
• C. RSTP alternate ports provide an alternate lower cost path to the root bridge.
• D. RSTP alternate ports block traffic while receiving superior BPDUs from a neighboring switch.

Answer: B,D

Explanation:
A is correct because RSTP alternate ports block traffic while receiving superior BPDUs from a neighboring switch. An alternate port is a backup port for a root port, which means it receives better BPDUs from another bridge than the current root port1. However, an alternate port does not forward any traffic, as it is in a discarding state2. It only listens to BPDUs and waits for the root port to fail. If the root port fails, the alternate port can immediately transition to a forwarding state and become the new root port1.
C is correct because RSTP alternate ports provide an alternate higher cost path to the root bridge. An alternate port is selected based on the same criteria as the root port, which are the lowest bridge ID, the lowest path cost, the lowest sender port ID, and the lowest receiver port ID3. However, an alternate port receives a higher cost BPDU than the root port, otherwise it would be the root port itself1. Therefore, an alternate port provides an alternate higher cost path to the root bridge than the root port.

NEW QUESTION # 24
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. local preference
• B. MED
• C. origin
• D. next-hop

Answer: A

Explanation:
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.

NEW QUESTION # 25
Exhibit.

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

• A. R4
• B. R2
• C. R1
• D. R3

Answer: A

Explanation:
Explanation
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)

NEW QUESTION # 26
Which two statements about redundant trunk groups on EX Series switches are correct? (Choose two.)

• A. If the active link fails, then the secondary link automatically takes over.
• B. Redundant trunk groups use spanning tree to provide loop-free redundant uplinks.
• C. Redundant trunk groups load balance traffic across two designated uplink interfaces.
• D. Layer 2 control traffic is permitted on the secondary link.

Answer: A,D

Explanation:
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.

NEW QUESTION # 27
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. IP subnets are not a /30 address.
• B. The lo0 interface is not included as an IS-IS interface.
• C. MTU is not at least 1492 bytes.
• D. The Level 2 routers have mismatched areas.

Answer: B,C

Explanation:
Explanation
Option A suggests that the MTU is not at least 1492 bytes. This is correct because IS-IS requires a minimum MTU of 1492 bytes to establish adjacencies1. If the MTU is less than this, IS-IS adjacencies will not be established1.
Option D suggests that the lo0 interface is not included as an IS-IS interface. This is also correct because the loopback interface (lo0) is typically used as the router ID in IS-IS1. If the loopback interface is not included in IS-IS, it could prevent IS-IS adjacencies from being established1.
Therefore, options A and D are correct.

NEW QUESTION # 28
Which statement is correct about controlling the routes installed by a RIB group?

• A. Only routes in the last table are installed.
• B. An import policy is applied to the RIB group.
• C. A firewall filter must be configured to install routes in the RIB groups.
• D. An export policy is applied to the RIB group.

Answer: B

Explanation:
Explanation
A RIB group is a configuration that allows a routing protocol to install routes into multiple routing tables in Junos OS. 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 or group. A RIB group can also include an import-policy statement, which specifies one or more policies to control which routes are imported into the destination routing table or group1.
An import policy is a policy statement that defines the criteria for accepting or rejecting routes from the source routing table. An import policy can also modify the attributes of the imported routes, such as preference, metric, or community. An import policy can be applied to a RIB group by using the import-policy statement under the [edit routing-options rib-groups] hierarchy level1.
Therefore, option A is correct, because an import policy is applied to the RIB group to control which routes are installed in the destination routing table or group. Option B is incorrect, because all routes in the source routing table are imported into the destination routing table or group, unless filtered by an import policy.
Option C is incorrect, because a firewall filter is not used to install routes in the RIB groups; a firewall filter is used to filter packets based on various criteria. Option D is incorrect, because an export policy is not applied to the RIB group; an export policy is applied to a routing protocol to control which routes are advertised to other devices.
References:
1: rib-groups | Junos OS | Juniper Networks

NEW QUESTION # 29
Which two statements about redundant trunk groups on EX Series switches are correct? (Choose two.)

• A. If the active link fails, then the secondary link automatically takes over.
• B. Redundant trunk groups load-balance traffic across two designated uplink interfaces.
• C. Redundant trunk groups must be connected to the same aggregation switch.
• D. Layer 2 control traffic is permitted on the secondary link

Answer: A,C

Explanation:
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.

NEW QUESTION # 30
Which three protocols support BFD? (Choose three.)

• A. LACP
• B. RSTP
• C. BGP
• D. OSPF
• E. FTP

Answer: A,C,D

Explanation:
Explanation
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.
According to the Juniper Networks documentation, the following protocols support BFD on Junos OS devices1:
BGP: BFD can be used to monitor the connectivity between BGP peers and trigger a session reset if a failure is detected. BFD can be configured for both internal and external BGP sessions, as well as for IPv4 and IPv6 address families2.
OSPF: BFD can be used to monitor the connectivity between OSPF neighbors and trigger a state change if a failure is detected. BFD can be configured for both OSPFv2 and OSPFv3 protocols, as well as for point-to-point and broadcast network types3.
LACP: BFD can be used to monitor the connectivity between LACP members and trigger a link state change if a failure is detected. BFD can be configured for both active and passive LACP modes, as well as for static and dynamic LAGs4.
Other protocols that support BFD on Junos OS devices are:
IS-IS: BFD can be used to monitor the connectivity between IS-IS neighbors and trigger a state change if a failure is detected. BFD can be configured for both level 1 and level 2 IS-IS adjacencies, as well as for point-to-point and broadcast network types.
RIP: BFD can be used to monitor the connectivity between RIP neighbors and trigger a route update if a failure is detected. BFD can be configured for both RIP version 1 and version 2 protocols, as well as for IPv4 and IPv6 address families.
VRRP: BFD can be used to monitor the connectivity between VRRP routers and trigger a priority change if a failure is detected. BFD can be configured for both VRRP version 2 and version 3 protocols, as well as for IPv4 and IPv6 address families.
The protocols that do not support BFD on Junos OS devices are:
RSTP: RSTP is a spanning tree protocol that provides loop prevention and rapid convergence in layer 2 networks. RSTP does not use BFD to detect link failures, but relies on its own hello mechanism that sends BPDU packets every 2 seconds by default.
FTP: FTP is an application layer protocol that is used to transfer files between hosts over a TCP connection. FTP does not use BFD to detect connection failures, but relies on TCP's own retransmission and timeout mechanisms.
References:
1: [Configuring Bidirectional Forwarding Detection] 2: [Configuring Bidirectional Forwarding Detection for BGP] 3: [Configuring Bidirectional Forwarding Detection for OSPF] 4: [Configuring Bidirectional Forwarding Detection for Link Aggregation Control Protocol] : [Configuring Bidirectional Forwarding Detection for IS-IS] : [Configuring Bidirectional Forwarding Detection for RIP] : [Configuring Bidirectional Forwarding Detection for VRRP] : [Understanding Rapid Spanning Tree Protocol] : [Understanding FTP]

NEW QUESTION # 31
Exhibit

You are troubleshooting an issue where traffic to 192.168.10.0/24 is being sent to R1 instead of your desired path through R2.
Referring to the exhibit, what is the reason for the problem?

• A. R1's route is the best path due to the shorter AS path.
• B. R2's route is not the best path due to a lower origin code.
• C. R1's route is the best path due to a higher local preference
• D. R2's route is not the best path due to loop prevention.

Answer: C

Explanation:
The exhibit shows the output of the command show ip bgp, which displays information about the BGP routes in the routing table1. The output shows two routes for the destination 192.168.10.0/24, one from R1 and one from R2.
The route from R1 has a local preference of 200, while the route from R2 has a local preference of
100. Local preference is a BGP attribute that indicates the degree of preference for a route within an autonomous system (AS)2. A higher local preference means a more preferred route2.
BGP uses a best path selection algorithm to choose the best route for each destination among multiple paths. The algorithm compares different attributes of the routes in a specific order of precedence3. The first attribute that is compared is weight, which is a Cisco-specific attribute that is local to the router3. If the weight is equal or not set, the next attribute that is compared is local preference3.
In this case, both routes have the same weight of 0, which means that they are learned from external BGP (eBGP) peers3. Therefore, the next attribute that is compared is local preference. Since R1's route has a higher local preference than R2's route, it is chosen as the best path and installed in the routing table3. The other attributes, such as origin code and AS path, are not considered in this case.

NEW QUESTION # 32
Exhibit

Which command displays the output shown in the exhibit?

• A. show route forwarding-table
• B. show ethernet-switching table
• C. show route forwarding-table family ethernet-switching
• D. show ethernet-switching table extensive

Answer: B

Explanation:
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.

NEW QUESTION # 33
Which two statements are correct about using firewall filters on EX Series switches? (Choose two.)

• A. You can only apply firewall filters to Layer 2 traffic on an EX Series switch.
• B. You can deploy both stateless and stateful firewall filters on an EX Series switch.
• C. You can deploy only stateless firewall filters on an EX Series switch.
• D. You can apply firewall filters to both Layer 2 and Layer 3 traffic on an EX Series switch.

Answer: C,D

Explanation:
A is correct because you can deploy only stateless firewall filters on an EX Series switch. A stateless firewall filter is a filter that evaluates each packet individually based on the header information, such as source and destination addresses, protocol, and port numbers1. A stateless firewall filter does not keep track of the state or context of a packet flow, such as the sequence number, flags, or sessioninformation1. EX Series switches support only stateless firewall filters, which are also called access control lists (ACLs) or packet filters2.
C is correct because you can apply firewall filters to both Layer 2 and Layer 3 traffic on an EX Series switch. Layer 2 traffic is traffic that is switched within a VLAN or a bridge domain, while Layer 3 traffic is traffic that is routed between VLANs or networks3. EX Series switches support three types of firewall filters: port (Layer 2) firewall filters, VLAN firewall filters, and router (Layer 3) firewall filters4. You can apply these filters to different interfaces and directions to control the traffic entering or exiting the switch.

NEW QUESTION # 34
Which two statements about BGP facilitate the prevention of routing loops between two autonomous systems?
(Choose two.)

• A. EBGP routers will prepend their AS number when advertising routes to their neighbors
• B. EBGP routers will drop routes that contain their own AS number in the AS_PATH
• C. EBGP routers will only accept routes that contain their own AS number in the AS_PATH.
• D. EBGP routers will append their AS number when advertising routes to their neighbors.

Answer: B,D

Explanation:
Explanation
BGP (Border Gateway Protocol) is a protocol designed to exchange routing and reachability information among autonomous systems (AS) on the internet1.
Option A is correct. When an EBGP router advertises routes to its neighbors, it appends its AS number to the AS_PATH attribute1. This is a key mechanism in BGP to prevent routing loops1.
Option C is correct. BGP has a built-in loop prevention mechanism whereby if a BGP router detects its own AS in the AS_PATH attribute, it will drop the prefix and will not continue to advertise it2. This helps to prevent routing loops2.
Option B is incorrect. EBGP routers do not accept routes that contain their own AS number in the AS_PATH2. Instead, they drop such routes as part of the loop prevention mechanism2.
Option D is incorrect. While it's true that EBGP routers append their AS number when advertising routes, they do not prepend their AS number1. The term "prepend" in BGP usually refers to a technique used to influence path selection by artificially lengthening the AS_PATH3.

NEW QUESTION # 35
Which two BGP attributes must be supported by all BGP implementations and must be included in every update? (Choose two.)

• A. next hop
• B. MED
• C. community
• D. AS path

Answer: A,D

Explanation:
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.

NEW QUESTION # 36
What is a purpose of using a spanning tree protocol?

• A. to route IP packets
• B. to tunnel Ethernet frames
• C. to eliminate broadcast storms
• D. to look up MAC addresses

Answer: C

Explanation:
A broadcast storm is a network condition where a large number of broadcast packets are sent and received by multiple devices, causing congestion and performance degradation1. A broadcast storm can occur when there are loops in the network topology, meaning that there are multiple paths between two devices2.
A spanning tree protocol is a network protocol that prevents loops from being formed when switches or bridges are interconnected via multiple paths. It does this by creating a logical tree structure that spans all the devices in the network, and disabling or blocking the links that are not part of the tree, leaving a single active path between any two devices3.
By eliminating loops, a spanning tree protocol also eliminates broadcast storms, as broadcast packets will not be forwarded endlessly along the looped paths. Instead, broadcast packets will be sent only along the tree structure, reaching each device once and avoiding congestion3.

NEW QUESTION # 37
You implemented the MAC address limit feature with the shutdown action on all interfaces on your switch.
In this scenario, which statement is correct when a violation occurs?

• A. By default, the interface will continue to send and receive traffic for all connected devices after a violation has occurred.
• B. By default, you must manually clear the violation for the interface to send and receive traffic again.
• C. By default, the violation will automatically be cleared after 300 seconds and the interface will resume sending and receiving traffic for all learned devices.
• D. By default, devices that are learned before the violation occurs are still allowed to send and receive traffic through the specific interface.

Answer: B

Explanation:
Explanation
When the MAC address limit feature with the shutdown action is implemented on a switch, if a violation occurs, the interface is disabled and a system log entry is generated1. If the switch has been configured with the port-error-disable statement, the disabled interface recovers automatically upon expiration of the specified disable timeout1. However, if the switch has not been configured for auto-recovery from port error disabled conditions, you must manually clearthe violation by running the clear ethernet-switching port-error command for the interface to send and receive traffic again1. This explanation is based on the Enterprise Routing and Switching Specialist (JNCIS-ENT) documents and learning resources available at Juniper Networks1.

NEW QUESTION # 38
Which two types of tunnels are able to be created on all Junos devices? (Choose two.)

• A. IP-IP
• B. GRE
• C. STP
• D. IPsec

Answer: B,D

Explanation:
Explanation
Junos devices support various types of tunnels for different purposes12.
Option B is correct. Generic Routing Encapsulation (GRE) is a tunneling protocol that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links over an Internet Protocol network1. Junos devices support GRE tunnels1.
Option D is correct. IPsec (Internet Protocol Security) is a protocol suite for securing Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a communication session1. Junos devices support IPsec tunnels1.
Option A is incorrect. Spanning Tree Protocol (STP) is not a type of tunnel. It's a network protocol designed to prevent loops in a bridged Ethernet local area network2.
Option C is incorrect. While Junos devices do support IP-IP (also known as IP tunneling), it's not supported on all Junos devices1.

NEW QUESTION # 39
After receiving a BGP route, which two conditions are verified by the receiving router to ensure that the received route is valid? (Choose two)

• A. The next hop is reachable.
• B. The loops do not exist.
• C. The AS-path length is greater than 0.
• D. The local preference is greater than 0.

Answer: A,B

Explanation:
B is correct because the loops do not exist is one of the conditions that are verified by the receiving router to ensure that the received BGP route is valid. A loop in BGP means that a route has been advertised by the same AS more than once, which can cause routing instability and inefficiency1. To prevent loops, BGP uses the AS-path attribute, which lists the AS numbers that a route has traversed from the origin to the destination2. The receiving router checks the AS-path attribute of the received route and discards it if it finds its own AS number in the list2. This way, BGP avoids accepting routes that contain loops.
C is correct because the next hop is reachable is one of the conditions that are verified by the receiving router to ensure that the received BGP route is valid. The next hop is the IP address of the next router that is used to forward packets to the destination network3. The receiving router checks the next hop attribute of the received route and verifies that it has a valid route to reach it3. If the next hop is not reachable, the received route is not usable and is rejected by the receiving router3. This way, BGP ensures that only feasible routes are accepted.

NEW QUESTION # 40
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