Latest [Dec 13, 2025] JN0-351 Exam Questions – Valid JN0-351 Dumps Pdf
JN0-351 Practice Test Questions Answers Updated 67 Questions
NEW QUESTION # 27
Which three protocols support BFD? (Choose three.)
- A. BGP
- B. FTP
- C. LACP
- D. OSPF
- E. RSTP
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 # 28
What are two reasons for creating multiple areas in OSPF? (Choose two.)
- A. to increase the number of adjacencies in the backbone
- B. to reduce LSA flooding across the network
- C. to reduce the convergence time
- D. to increase the size of the LSDB
Answer: B,C
Explanation:
Explanation
Option A is correct. Creating multiple areas in OSPF can help to reduce the convergence time . This is because changes in one area do not affect other areas, so fewer routers need to run the SPF algorithm in response to a change.
Option D is correct. Creating multiple areas in OSPF can help to reduce Link State Advertisement (LSA) flooding across the network. This is because LSAs are not flooded out of their area of origin.
NEW QUESTION # 29
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 lower cost path to the root bridge.
- C. RSTP alternate ports block traffic while receiving superior BPDUs from a neighboring switch.
- D. RSTP alternate ports provide an alternate higher cost path to the root bridge.
Answer: C,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 # 30
Which two statements about BGP facilitate the prevention of routing loops between two autonomous systems?
(Choose two.)
- A. EBGP routers will drop routes that contain their own AS number in the AS_PATH
- B. EBGP routers will append their AS number when advertising routes to their neighbors.
- C. EBGP routers will prepend their AS number when advertising routes to their neighbors
- D. EBGP routers will only accept routes that contain their own AS number in the AS_PATH.
Answer: A,B
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 # 31
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 routers are exchanging IPv4 routes.
- C. The R1 is configured for AS 65400.
- D. The BGP session is not established.
Answer: C,D
Explanation:
Explanation
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.
NEW QUESTION # 32
Exhibit
What does the * indicate in the output shown in the exhibit?
- A. All interfaces have elected a root bridge.
- B. The interface is active.
- C. The switch ports have a router attached.
- D. The interface is down.
Answer: B
Explanation:
The exhibit shows the output of the command show vlans brief, which displays brief information about VLANs and their associated interfaces1.
The output has four columns: Routing instance, VLAN name, Interfaces, and Tagging.
The * symbol indicates that the interface is active, meaning that it is up and forwarding traffic1. This can be verified by the command , which displays the status of the interfaces2.
NEW QUESTION # 33
Exhibit
You are receiving the BGP route shown in the exhibit from four different upstream ISPs.
Referring to the exhibit, which ISP will be selected as the active path?
- A. ISP 3
- B. ISP 2
- C. ISP1
- D. ISP 4
Answer: D
Explanation:
Explanation
In BGP, the path selection process is based on a set of attributes1. The process starts by preferring the path with the highest weight, then the highest local preference, then the locally originated routes, and so on1. If all these attributes are the same, then it prefers the path with the shortest AS path1.
Referring to the exhibit, all four ISPs have the same weight, local preference, and origin1. However, ISP 4 has the shortest AS path1. Therefore, ISP 4 will be selected as the active path. So, option C is correct.
NEW QUESTION # 34
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 imported into the ispi . inet. 0 route table.
- B. The ISPI . inet. 0 route table will be imported into the inet. 0 route table.
- C. The ISPI . inet. 0 route table will be completely overwritten by the inet. o route table.
- D. The inet. 0 route table will be completely overwritten by the ispi . inet. 0 route table.
Answer: A
Explanation:
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)]
NEW QUESTION # 35
You are asked to create a new firewall filter to evaluate Layer 3 traffic that is being sent between VLANs. In this scenario, which two statements are correct? (Choose two.)
- A. You should apply the firewall filter to the appropriate VLAN.
- B. You should create a family inet firewall filter with the appropriate match criteria and actions.
- C. You should apply the firewall filter to the appropriate IRB interface.
- D. You should create a family Ethernet-switching firewall filter with the appropriate match criteria and actions.
Answer: B,C
Explanation:
Explanation
A firewall filter is a configuration that defines the rules that determine whether to forward or discard packets at specific processing points in the packet flow. A firewall filter can also modify the attributes of the packets, such as priority, marking, or logging. A firewall filter can be applied to various interfaces, protocols, or routing instances on a Juniper device1.
A firewall filter has a family attribute, which specifies the type of traffic that the filter can evaluate. The family attribute can be one of the following: inet, inet6, mpls, vpls, iso, or ethernet-switching2. The family inet firewall filter is used to evaluate IPv4 traffic, which is the most common type of Layer 3 traffic on a network.
To create a family inet firewall filter, you need to specify the appropriate match criteria and actions for each term in the filter. The match criteria can include various fields in the IPv4 header, such as source address, destination address, protocol, port number, or DSCP value. The actions can include accept, discard, reject, count, log, policer, or next term3.
To apply a firewall filter to Layer 3 traffic that is being sent between VLANs, you need to apply the filter to the appropriate IRB interface. An IRB interface is an integrated routing and bridging interface that provides Layer 3 functionality for a VLAN on a Juniper device. An IRB interface has an IP address that acts as the default gateway for the hosts in the VLAN. An IRB interface can also participate in routing protocols and forward packets to other VLANs or networks4.
Therefore, option C is correct, because you should create a family inet firewall filter with the appropriate match criteria and actions. Option D is correct, because you should apply the firewall filter to the appropriate IRB interface.
Option A is incorrect, because you should not create a family ethernet-switching firewall filter with the appropriate match criteria and actions. A family ethernet-switching firewall filter is used to evaluate Layer 2 traffic on a Juniper device. A family ethernet-switching firewall filter can only match on MAC addresses or VLAN IDs, not on IP addresses or protocols5.
Option B is incorrect, because you should not apply the firewall filter to the appropriate VLAN. A VLAN is a logical grouping of hosts that share the same broadcast domain on a Layer 2 network. A VLAN does not have an IP address or routing capability. A firewall filter cannot be applied directly to a VLAN; it must be applied to an interface that belongs to or connects to the VLAN6.
References:
1: Firewall Filters Overview 2: Configuring Firewall Filters 3: Configuring Firewall Filter Match Conditions and Actions 4: Understanding Integrated Routing and Bridging Interfaces 5: Configuring Ethernet-Switching Firewall Filters 6: Understanding VLANs
NEW QUESTION # 36
Exhibit.
Which router will become the OSPF BDR if all routers are powered on at the same time?
- A. R4
- B. R3
- C. R2
- D. R1
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 # 37
What is the maximum allowable MTU size for a default GRE tunnel without IPv4 traffic fragmentation?
- A. 1480 bytes
- B. 1496 bytes
- C. 1476 bytes
- D. 1500 bytes
Answer: C
Explanation:
Explanation
The maximum allowable MTU size for a default GRE tunnel without IPv4 traffic fragmentation is 1476 bytes1. This is because GRE packets are formed by the addition of the original packets and the required GRE headers1. These headers are 24-bytes in length and since these headers are added to the original frame, depending on the original size of the packet we may run into IP MTU problems1. The most common IP MTU is 1500-bytes in length (Ethernet)1. When the tunnel is created, it deducts the 24-bytes it needs to encapsulate the passenger protocols and that is the IP MTU it will use1. For example, if we are forming a tunnel over FastEthernet (IP MTU 1500)the IOS calculates the IP MTU on the tunnel as: 1500-bytes from Ethernet -
24-bytes for the GRE encapsulation = 1476-Bytes1.
NEW QUESTION # 38
Exhibit
Which command displays the output shown in the exhibit?
- A. show route forwarding-table family ethernet-switching
- B. show route forwarding-table
- C. show ethernet-switching table
- D. show ethernet-switching table extensive
Answer: C
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 # 39
An update to your organization's network security requirements document requires management traffic to be isolated in a non-default routing-instance. You want to implement this requirement on your Junos-based devices.
Which two commands enable this behavior? (Choose two.)
- A. set system management-instance
- B. set routing-instances mgmtjunoa interface ge-0/0/0.0
- C. set routing-instances mgmt_junos
- D. set routing-instances mgmt_junos interface em1
Answer: A,C
Explanation:
Explanation
To isolate management traffic in a non-default routing-instance on Junos-based devices, you can use the set system management-instance and set routing-instances mgmt_junos commands12.
set system management-instance: This command associates the management interface (usually named fxp0 or em0 for Junos OS, or re0:mgmt-* or re1:mgmt-* for Junos OS Evolved) with the non-default virtual routing and forwarding (VRF) instance1. After you configure the non-default management VRF instance, management traffic no longer has to share a routing table with other control traffic or protocol traffic1.
set routing-instances mgmt_junos: This command creates a new routing instance named mgmt_junos. The name of the dedicated management VRF instance is reserved and hardcoded as mgmt_junos; you cannot configure any other routing instance by the name mgmt_junos1.
Therefore, options C and D are correct. Options A and B are not correct because they attempt to assign an interface to the mgmt_junos routing instance, which is not necessary for isolating management traffic1.
NEW QUESTION # 40
Two routers share the same highest priority and start time.
- A. The router with the highest router ID becomes the DR
- B. The routers perform another DR election.
- C. In this situation, what is evaluated next when determining the designated router? The router with the lowest router ID become the DR.
- D. The router with the highest MAC address become the DR
Answer: A
Explanation:
According to the OSPF protocol, the designated router (DR) is the router that acts as the focal point for exchanging routing information on a multi-access network segment, such as a LAN1. The DR election process is based on the following criteria, in order of precedence1:
The router with the highest OSPF priority becomes the DR. The default priority is 1, and a priority of 0 means the router will not participate in the election.
If there is a tie in priority, the router with the highest router ID becomes the DR. The router ID is a 32-bit number that uniquely identifies a router in an OSPF domain. It can be manually configured or automatically derived from the highest IP address of a loopback interface or a physical interface.
If there is a tie in router ID, the router that was first to become an OSPF neighbor becomes the DR.
In your scenario, two routers share the same highest priority and start time. This means that they have equal chances of becoming the DR based on the first and third criteria. Therefore, the second criterion will be used to break the tie, which is the router ID. The router with the highest router ID will become the DR, and the other router will become the backup designated router (BDR), which is ready to take over the role of DR if it fails1.
NEW QUESTION # 41
Which two types of tunnels are able to be created on all Junos devices? (Choose two.)
- A. STP
- B. GRE
- C. IP-IP
- 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 # 42
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. origin
- C. local preference
- D. next-hop
Answer: C
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 # 43
You need to configure a LAG between your switches. In this scenario, which two statements are correct?
(Choose two.)
- A. Member links are not required to be contiguous ports.
- B. Member links are required to be contiguous ports.
- C. Duplex and speed settings are not required to match on both participating devices.
- D. Duplex and speed settings are required to match on both participating devices.
Answer: A,D
Explanation:
B is correct because duplex and speed settings are required to match on both participating devices. According to the Juniper Networks documentation1, all the interfaces in a LAG must have the same speed and be in full-duplex mode. This ensures that the LAG can operate as a single logical link without any performance or compatibility issues.
C is correct because member links are not required to be contiguous ports. According to the Juniper Networks documentation2, you can group any Ethernet interfaces on a switch into a LAG, regardless of their physical location or slot number. This provides flexibility and scalability for configuring LAGs on switches.
NEW QUESTION # 44
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