[Sep-2025] Updated and Accurate JN0-351 Questions & Answers for passing the exam Quickly

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NEW QUESTION # 20
You are an operator for a network running 1S-IS. Two routers are failing to form an adjacency. What are two reasons for this problem? (Choose two.)

• A. The family iso configuration is missing from the adjacency interface.
• B. There are mismatched router IDs on the L2 routers.
• C. There is no configured ISO address on any IS-IS interface.
• D. There is a mismatched area ID between the L2 routers.

Answer: A,C

Explanation:
Explanation
The two reasons for the failure to form an adjacency in a network running IS-IS could be:
B: There is no configured ISO address on any IS-IS interface. IS-IS requires each router interface to have an ISO address configured. Without this address, the routers cannot form an adjacency1.
D: The family iso configuration is missing from the adjacency interface. The 'family iso' configuration is essential for IS-IS to function correctly. If this configuration is missing from the adjacency interface, it could prevent the formation of an adjacency1.
These explanations are based on the Enterprise Routing and Switching Specialist (JNCIS-ENT) documents and learning resources available at Juniper Networks23.

NEW QUESTION # 21
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 is set too high.
• D. The BFD liveness must be configured on the BGP group.

Answer: B

Explanation:
Explanation
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.

NEW QUESTION # 22
What is the default keepalive time for BGP?

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

Answer: C

Explanation:
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.

NEW QUESTION # 23
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 violation will automatically be cleared after 300 seconds and the interface will resume sending and receiving traffic for all learned devices.
• B. By default, devices that are learned before the violation occurs are still allowed to send and receive traffic through the specific interface.
• C. By default, you must manually clear the violation for the interface to send and receive traffic again.
• D. By default, the interface will continue to send and receive traffic for all connected devices after a violation has occurred.

Answer: C

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 # 24
Exhibit

Referring to the exhibit, which two configuration changes must you apply for packets to reach from R1 to R3 using IS-IS? (Choose two.)

• A. On R3 disable Level 2 on the ge-0/0/4 interface.
• B. On R1, disable Level 2 on the ge-0/0/1 interface.
• C. On R1, enable Level 1 on the ge-0/0/1 interface.
• D. On R3 enable Level 1 on the ge-0/0/4 interface

Answer: C,D

Explanation:
Explanation
A: On R1, enable Level 1 on the ge-0/0/1 interface. In IS-IS, both levels (Level 1 and Level 2) are enabled by default when you enable IS-IS on an interface1. Level 1 systems route within an area2. If the destination is outside an area, Level 1 systems route toward a Level 2 system2. Therefore, enabling Level 1 on the ge-0/0/1 interface on R1 would allow packets to reach from R1 to R3.
D: On R3 enable Level 1 on the ge-0/0/4 interface Similarly, enabling Level 1 on the ge-0/0/4 interface on R3 would allow packets to reach from R1 to R3.
These explanations are based on the IS-IS configuration documents and learning resources available at Juniper Networks1 and Cisco34.

NEW QUESTION # 25
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. static route using qualified next hops
• B. aggregate route
• C. static route using the resolve feature
• D. generate route

Answer: B

Explanation:
Explanation
In this scenario, you should create an 1. 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.

NEW QUESTION # 26
Which two types of tunnels are able to be created on all Junos devices? (Choose two.)

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

Answer: B,C

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 # 27
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 max-age must be increased to 20
• B. The hello-time must be increased.
• C. The bridge priority for EX-4 must be set at 4000.
• D. The force-version must be removed.

Answer: D

Explanation:
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.

NEW QUESTION # 28
Which two statements are correct about using firewall filters on EX Series switches? (Choose two.)

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

Answer: A,B

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 # 29
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. R2's route is not the best path due to a lower origin code.
• B. R2's route is not the best path due to loop prevention.
• C. R1's route is the best path due to a higher local preference
• D. R1's route is the best path due to the shorter AS path.

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 # 30
Exhibit.

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

• A. R2
• B. R1
• C. R3
• D. R4

Answer: D

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 # 31
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. BFD must be used on the stateless tunneling protocols.
• C. Keepalives must be used on stateless tunneling protocols.
• D. All intermediary devices must have a route to the tunnel endpoints.

Answer: A,D

Explanation:
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.

NEW QUESTION # 32
Which statement is correct about controlling the routes installed by a RIB group?

• A. A firewall filter must be configured to install routes in the RIB groups.
• B. An import policy is applied to the RIB group.
• C. Only routes in the last table are installed.
• 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 # 33
Which two statements are true about the default VLAN on Juniper switches? (Choose two.)

• A. The default VLAN ID is not visible.
• B. The default VLAN ID is not assigned to any interface.
• C. The default VLAN ID can be changed.
• D. The default VLAN is set to a VLAN ID of 1 by default

Answer: C,D

Explanation:
Explanation
On Juniper switches, the default VLAN is set to a VLAN ID of 1 by default12. This means that all interfaces on the switch are members of VLAN 1 until they are specifically assigned to another VLAN12. Therefore, option A is correct.
The default VLAN ID can be changed12. This allows network administrators to configure the switch to use a different VLAN as the default, if necessary12. Therefore, option D is correct.

NEW QUESTION # 34
Two routers share the same highest priority and start time.

• A. In this situation, what is evaluated next when determining the designated router? The router with the lowest router ID become the DR.
• B. The router with the highest MAC address become the DR
• C. The router with the highest router ID becomes the DR
• D. The routers perform another DR election.

Answer: C

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 # 35
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 routing-instances mgmtjunoa interface ge-0/0/0.0
• B. set routing-instances mgmt_junos
• C. set system management-instance
• D. set routing-instances mgmt_junos interface em1

Answer: B,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 # 36
Which two mechanisms are part of building and maintaining a Layer 2 bridge table? (Choose two.)

• A. blocking
• B. listening
• 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 # 37
Which two events cause a router to advertise a connected network to OSPF neighbors? (Choose two.)

• A. When an OSPF adjacency is established.
• B. When an interface has the OSPF passive option enabled.
• C. When a static route to the 224.0.0.5 address is created.
• D. When a static route to the 224.0.0.6 address is created.

Answer: A,C

Explanation:
A is correct because when an OSPF adjacency is established, a router will advertise a connected network to OSPF neighbors. An OSPF adjacency is a logical relationship between two routers that agree to exchange routing information using the OSPF protocol1. To establish an OSPF adjacency, the routers must be in the same area, have compatible parameters, and exchange hello packets1. Once an OSPF adjacency is formed, the routers will exchange database description (DBD) packets, which contain summaries of their link-state databases (LSDBs)1. The LSDBs include information about the connected networks and their costs2. Therefore, when an OSPF adjacency is established, a router will advertise a connected network to OSPF neighbors through DBD packets.
D is correct because when a static route to the 224.0.0.5 address is created, a router will advertise a connected network to OSPF neighbors. The 224.0.0.5 address is the multicast address for all OSPF routers3. A static route to this address can be used to send OSPF hello packets to all OSPF neighbors on a network segment3. This can be useful when the network segment does not support multicast or when the router does not have an IP address on the segment3. When a static route to the 224.0.0.5 address is created, the router will send hello packets to this address and establish OSPF adjacencies with other routers on the segment3. As explained above, once an OSPF adjacency is formed, the router will advertise a connected network to OSPF neighbors through DBD packets.

NEW QUESTION # 38
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.

Answer: A,D

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 # 39
Which statement about aggregate routes is correct?

• A. Aggregate routes are automatically generated for all of the subnets in a routing table.
• B. Aggregate routes are used for advertising summarized network prefixes.
• C. Aggregate routes can only be used for static routing but not for dynamic routing protocols.
• D. Aggregate routes are always preferred over more specific routes, even when the specific routes have a better path.

Answer: B

Explanation:
Explanation
Aggregate routes are used for advertising summarized network prefixes12. 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 D is correct. Options A, B, and C are not correct because:
Aggregate routes can be used with both static routing and dynamic routing protocols1.
Aggregate routes are not automatically generated for all of the subnets in a routing table. They need to be manually configured1.
Aggregate routes are not always preferred over more specific routes. The route selection process in Junos OS considers several factors, including route preference and metric, before determining the active route1.

NEW QUESTION # 40
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