JN0-351認定の有効な試験問題集解答学習ガイド！（最新の67問題)
JN0-351問題集で時間限定！無料アクセスせよ
質問 # 35
Exhibit
You have configured a GRE tunnel. To reduce the risk of dropping traffic, you have configured a keepalive OAM probe to monitor the state of the tunnel; however, traffic drops are still occurring.
Referring to the exhibit, what is the problem?
- A. The hold-time value must be two times the keepalive-time value
- B. The "event link-adjacency-loss" option must be set.
- C. For GRE tunnels, the OAM protocol requires that the BFD protocols also be used.
- D. LLDP needs to be removed from the gr-1/1/10.1 interface.
正解：A
解説：
Explanation
A keepalive OAM probe is a mechanism that can be used to monitor the state of a GRE tunnel and detect any failures in the tunnel path. A keepalive OAM probe consists of sending periodic packets from one end of the tunnel to the other and expecting a reply. If no reply is received within a specified time, the tunnel is considered down and the line protocol of the tunnel interface is changed to down1.
To configure a keepalive OAM probe for a GRE tunnel, you need to specify two parameters: the keepalive-time and the hold-time. The keepalive-time is the interval between each keepalive packet sent by the local router. The hold-time is the maximum time that the local router waits for a reply from the remote router before declaring the tunnel down2.
According to the Juniper Networks documentation, the hold-time value must be two times the keepalive-time value for a GRE tunnel2. This is because the hold-time value must account for both the round-trip time of the keepalive packet and the processing time of the remote router. If the hold-time value is too small, it may cause false positives and unnecessary tunnel flaps.
In the exhibit, the configuration shows that the keepalive-time is set to 10 seconds and the hold-time is set to
15 seconds for the gr-1/1/10.1 interface. This means that the local router will send a keepalive packet every 10 seconds and will wait for 15 seconds for a reply from the remote router. However, this hold-time value is not two times the keepalive-time value, which violates the recommended configuration. This may cause traffic drops if the remote router takes longer than 15 seconds to reply.
Therefore, option D is correct, because the hold-time value must be two times the keepalive-time value for a GRE tunnel. Option A is incorrect, because BFD is not required for GRE tunnels; BFD is another protocol that can be used to monitor tunnels, but it is not compatible with GRE keepalives3. Option B is incorrect, because the "event link-adjacency-loss" option is not related to GRE tunnels; it is an option that can be used to trigger an action when a link goes down4. Option C is incorrect, because LLDP does not need to be removed from the gr-1/1/10.1 interface; LLDP is a protocol that can be used to discover neighboring devices and their capabilities, but it does not interfere with GRE tunnels5.
References:
1: Configuring Keepalive Time and Hold time for a GRE Tunnel Interface 2: keepalive | Junos OS | Juniper Networks 3: Configuring Bidirectional Forwarding Detection 4: event link-adjacency-loss | Junos OS | Juniper Networks 5: Understanding Link Layer Discovery Protocol
質問 # 36
Which two types of tunnels are able to be created on all Junos devices? (Choose two.)
- A. GRE
- B. STP
- C. IPsec
- D. IP-IP
正解：A、C
解説：
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.
質問 # 37
You are asked to connect an IP phone and a user computer using the same interface on an EX Series switch.
The traffic from the computer does not use a VLAN tag, whereas the traffic from the IP phone uses a VLAN tag.
Which feature enables the interface to receive both types of traffic?
- A. MAC limiting
- B. voice VLAN
- C. native VLAN
- D. DHCP snooping
正解：B
解説：
Explanation
The feature that enables an interface on an EX Series switch to receive both untagged traffic (from the computer) and tagged traffic (from the IP phone) is the voice VLAN12.
The voice VLAN feature in EX-series switches enables access ports to accept both data (untagged) and voice (tagged) traffic and separate that traffic into different VLANs12. This allows the switch to differentiate between voice and data traffic, ensuring that voice traffic can be treated with a higher priority12. Therefore, option D is correct.
質問 # 38
What is the default MAC age-out timer on an EX Series switch?
- A. 30 seconds
- B. 300 minutes
- C. 300 seconds
- D. 30 minutes
正解：C
解説：
Explanation
The default MAC age-out timer on an EX Series switch is 300 seconds12. The MAC age-out timer is the maximum time that an entry can remain in the MAC table before it "ages out," or is removed31. This configuration can influence efficiency of network resource use by affecting the amount of traffic that is flooded to all interfaces1. When traffic is received for MAC addresses no longer in the Ethernet routing table, the router floods the traffic to all interfaces1.
質問 # 39
You are asked to connect an IP phone and a user computer using the same interface on an EX Series switch.
The traffic from the computer does not use a VLAN tag, whereas the traffic from the IP phone uses a VLAN tag.
Which feature enables the interface to receive both types of traffic?
- A. MAC limiting
- B. voice VLAN
- C. native VLAN
- D. DHCP snooping
正解：B
解説：
Explanation
The feature that enables an interface on an EX Series switch to receive both untagged traffic (from the computer) and tagged traffic (from the IP phone) is the voice VLAN12.
The voice VLAN feature in EX-series switches enables access ports to accept both data (untagged) and voice (tagged) traffic and separate that traffic into different VLANs12. This allows the switch to differentiate between voice and data traffic, ensuring that voice traffic can be treated with a higher priority12. Therefore, option D is correct.
質問 # 40
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 forwarding routing instance type.
- B. FBF uses the no-forwarding routing instance type.
- C. RIB groups are used to hide routes in the inet. 0 routing table.
- D. RIB groups are used to copy routes from the inet. o routing table.
正解：A、D
解説：
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.
質問 # 41
Which statement is correct about the storm control feature?
- A. The storm control feature requires a special license on EX Series switches.
- B. The storm control feature is not supported on aggregate Ethernet interfaces.
- C. The storm control configuration only applies to traffic being sent between the forwarding and control plane.
- D. The storm control feature is enabled in the factory-default configuration on EX Series switches.
正解：D
解説：
Option A is correct. The storm control feature is enabled in the factory-default configuration on EX Series switches12. On EX2200, EX3200, EX3300, EX4200, and EX6200 switches, the factory default configuration enables storm control for broadcast and unknown unicast traffic on all switch interfaces2. On EX4300 switches, the factory default configuration enables storm control on all Layer 2 switch interfaces1.
Option B is incorrect. The storm control feature does not require a special license on EX Series switches34.
Option C is incorrect. There's no information available that suggests the storm control feature is not supported on aggregate Ethernet interfaces.
Option D is incorrect. The storm control configuration applies to traffic at the ingress of an interface5, not just between the forwarding and control plane.
質問 # 42
Refer to the exhibit.
Referring to the output shown in the exhibit, which statement is correct?
- A. The state is normal for a DRother neighbor
- B. An MTU mismatch exists between the OSPF neighbors.
- C. The state is normal for a DR neighbor.
- D. An area ID mismatch exists between the OSPF neighbors
正解：A
解説：
Explanation
In OSPF, the state of the neighbor relationship is determined by the exchange of OSPF packets between routers1. The state "2Way" as shown in the exhibit indicates that bi-directional communication has been established between the two OSPF routers1. This is the normal state for a neighbor that is not the Designated Router (DR) or Backup Designated Router (BDR) on a broadcast, non-broadcast multi-access (NBMA), or point-to-multipoint network1. These neighbors are often referred to as "DRothers"1. Therefore, option B is correct.
質問 # 43
What is the default keepalive time for BGP?
- A. 30 seconds
- B. 10 seconds
- C. 90 seconds
- D. 60 seconds
正解：D
解説：
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.
質問 # 44
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. R2's route is not the best path due to loop prevention.
- D. R1's route is the best path due to a higher local preference
正解：D
解説：
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.
質問 # 45
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. next-hop
- B. MED
- C. local preference
- D. origin
正解：C
解説：
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.
質問 # 46
Which two statements are correct about tunnels? (Choose two.)
- A. Tunnel endpoints must have a valid route to the remote tunnel endpoint.
- B. Tunnels add additional overhead to packet size.
- C. IP-IP tunnels are stateful.
- D. BFD cannot be used to monitor tunnels.
正解：A、B
解説：
Explanation
A tunnel is a connection between two computer networks, in which data is sent from one network to another through an encrypted link. Tunnels are commonly used to secure data communications between two networks or to connect two networks that use different protocols.
Option B is correct, because tunnel endpoints must have a valid route to the remote tunnel endpoint. A tunnel endpoint is the device that initiates or terminates a tunnel connection. For a tunnel to be established, both endpoints must be able to reach each other over the underlying network. This means that they must have a valid route to the IP address of the remote endpoint1.
Option D is correct, because tunnels add additional overhead to packet size. Tunnels work by encapsulating packets: wrapping packets inside of other packets. This means that the original packet becomes the payload of the surrounding packet, and the surrounding packet has its own header and trailer. The header and trailer of the surrounding packet add extra bytes to the packet size, which is called overhead. Overhead can reduce the efficiency and performance of a network, as it consumes more bandwidth and processing power2.
Option A is incorrect, because BFD can be used to monitor tunnels. BFD is a protocol that can be used to quickly detect failures in the forwarding path between two adjacent routers or switches. BFD can be integrated with various routing protocols and link aggregation protocols to provide faster convergence and fault recovery.
BFD can also be used to monitor the connectivity of tunnels, such as GRE, IPsec, or MPLS.
Option C is incorrect, because IP-IP tunnels are stateless. IP-IP tunnels are a type of tunnels that use IP as both the encapsulating and encapsulated protocol. IP-IP tunnels are simple and easy to configure, but they do not provide any security or authentication features. IP-IP tunnels are stateless, which means that they do not keep track of the state or status of the tunnel connection. Stateless tunnels do not require any signaling or negotiation between the endpoints, but they also do not provide any error detection or recovery mechanisms.
References:
1: What is Tunneling? | Tunneling in Networking 2: What Is Tunnel In Networking, Its Types, And Its Benefits? : [Configuring Bidirectional Forwarding Detection] : [IP-IP Tunneling]
質問 # 47
Exhibit
Referring to the exhibit, which statement is correct?
- A. The local device is the root bridge for this RSTP topology.
- B. The root bridge has not been elected for this RSTP topology.
- C. The root bridge is using a bridge priority of 4k.
- D. The local device is using a bridge priority of 4k.
正解：A
解説：
Explanation
In a Rapid Spanning Tree Protocol (RSTP) topology, the root bridge is determined by the switch with the lowest bridge priority value12. If all switches have the same priority, then the root bridge is assigned to the switch whose MAC address's hex value is the lowest2. The default bridge priority value is 3276832. However, without the actual exhibit, it's difficult to definitively determine which device is the root bridge. But based on the options provided, if we assume that the local device has a lower bridge priority or a lower MAC address than other devices in the network, then it could be considered as the root bridge for this RSTP topology45.
質問 # 48
What are two reasons for creating multiple areas in OSPF? (Choose two.)
- A. to reduce the convergence time
- B. to increase the number of adjacencies in the backbone
- C. to increase the size of the LSDB
- D. to reduce LSA flooding across the network
正解：A、D
解説：
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.
質問 # 49
What is a purpose of using a spanning tree protocol?
- A. to eliminate broadcast storms
- B. to tunnel Ethernet frames
- C. to route IP packets
- D. to look up MAC addresses
正解：A
解説：
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.
質問 # 50
Two routers share the same highest priority and start time.
- A. The router with the highest MAC address become the DR
- B. The router with the highest router ID becomes the DR
- 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 routers perform another DR election.
正解：B
解説：
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.
質問 # 51
In RSTP, which three port roles are associated with the discarding state? (Choose three.)
- A. disabled
- B. backup
- C. alternate
- D. designated
- E. root
正解：A、B、C
解説：
Explanation
In Rapid Spanning Tree Protocol (RSTP), there are several port roles that determine the behavior of the port in the spanning tree123. The roles include root, designated, alternate, backup, and disabled123.
The discarding state is associated with the backup, alternate, and disabled roles123. In a stable topology with consistent port roles throughout the network, RSTP ensures that every root port and designated port immediately transition to the forwarding state while all alternate and backup ports are always in the discarding state2. Disabled ports are also in the discarding state3.
Therefore, options B, C, and D are correct.
質問 # 52
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 mgmt_junos interface em1
- C. set routing-instances mgmtjunoa interface ge-0/0/0.0
- D. set routing-instances mgmt_junos
正解：A、D
解説：
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.
質問 # 53
You are a network operator who wants to add a second ISP connection and remove the default route to the existing ISP You decide to deploy the BGP protocol in the network.
What two statements are correct in this scenario? (Choose two.)
- A. IBGP peers advertise routes received from IBGP peers to other IBGP peers.
- B. IBGP updates the next-hop attribute to ensure reachability within an AS.
- C. EBGP peers advertise routes received from IBGP peers to other EBGP peers.
- D. IBGP peers advertise routes received from EBGP peers to other IBGP peers.
正解：B、D
解説：
A is correct because IBGP updates the next-hop attribute to ensure reachability within an AS. This is because the next-hop attribute is the IP address of the router that advertises the route to a BGP peer. If the next-hop attribute is not changed by IBGP, it would be the IP address of an external router, which may not be reachable by all routers within the AS. Therefore, IBGP updates the next-hop attribute to the IP address of the router that received the route from an EBGP peer1.
B is correct because IBGP peers advertise routes received from EBGP peers to other IBGP peers. This is because BGP follows the rule of advertising only the best route to a destination, and EBGP routes have a higher preference than IBGP routes. Therefore, IBGP peers advertise routes learned from an EBGP peer to all BGP peers, including both EBGP and IBGP peers1.
質問 # 54
Which statement about aggregate routes is correct?
- A. Aggregate routes are always preferred over more specific routes, even when the specific routes have a better path.
- 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 automatically generated for all of the subnets in a routing table.
正解：B
解説：
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.
質問 # 55
What are two characteristics of RSTP alternate ports? (Choose two.)
- A. RSTP alternate ports provide an alternate higher cost path to the root bridge.
- B. RSTP alternate ports block traffic while receiving superior BPDUs from a neighboring switch.
- C. RSTP alternate ports are active ports used to forward frames toward the root bridge.
- D. RSTP alternate ports provide an alternate lower cost path to the root bridge.
正解：A、B
解説：
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.
質問 # 56
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. Router IDs must match for an adjacency to form.
- B. R1 will be the BDR.
- C. R2 will be the BDR.
- D. At least three routers are required for a DR/BDR election
正解：B
解説：
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.
質問 # 57
......
Juniper JN0-351試験実践テスト問題：https://jp.fast2test.com/JN0-351-premium-file.html
JN0-351問題集で2023年最新のJuniper JN0-351試験問題：https://drive.google.com/open?id=1VoZkSBEyB_vEOR-5Z3xnYzAGqIIi1drD