Juniper JN0-351 Real Exam Questions
The questions for JN0-351 were last updated at Jul 24,2024.
- Exam Code: JN0-351
- Exam Name: Enterprise Routing and Switching, Specialist (JNCIS-ENT)
- Certification Provider: Juniper
- Latest update: Jul 24,2024
Question #1
Which statement is correct about controlling the routes installed by a RIB group?
- A . An import policy is applied to the RIB group.
- B . Only routes in the last table are installed.
- C . A firewall filter must be configured to install routes in the RIB groups.
- D . An export policy is applied to the RIB group.
Correct Answer: A
A
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.
Reference: 1: rib-groups | Junos OS | Juniper Networks
A
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.
Reference: 1: rib-groups | Junos OS | Juniper Networks
Question #2
Exhibit.
The ispi _ inet. 0 route table has currently no routes in it.
What will happen when you commit the configuration shown on the exhibit?
- A . The inet. 0 route table will be completely overwritten by the ispi . inet. 0 route table.
- B . The inet. 0 route table will be imported into the ispi . inet. 0 route table.
- C . The ISPI . inet. 0 route table will be completely overwritten by the inet. o route table.
- D . The ISPI . inet. 0 route table will be imported into the inet. 0 route table.
Correct Answer: B
B
Explanation:
The configuration shown in the exhibit is an example of a routing instance of type virtual-router. A routing instance is a collection of routing tables, interfaces, and routing protocol parameters that create a separate routing domain on a Juniper device1. A virtual-router routing instance allows administrators to divide a device into multiple independent virtual routers, each with its own routing table2.
The configuration also includes a rib-group statement, which is used to import routes from one routing table to another. A rib-group consists of an import-rib statement, which specifies the source routing table, and an export-rib statement, which specifies the destination routing table.
In this case, the rib-group name is inet-to-ispi, and the import-rib statement specifies inet.0 as the source routing table. The export-rib statement specifies ispi.inet.0 as the destination routing table.
This means that the routes from inet.0 will be imported into ispi.inet.0.
Therefore, the correct answer is B. The inet.0 route table will be imported into the ispi.inet.0 route table.
Reference:
1: Routing Instances Overview 2: Virtual Routing Instances : [rib-group (Routing Options)]
B
Explanation:
The configuration shown in the exhibit is an example of a routing instance of type virtual-router. A routing instance is a collection of routing tables, interfaces, and routing protocol parameters that create a separate routing domain on a Juniper device1. A virtual-router routing instance allows administrators to divide a device into multiple independent virtual routers, each with its own routing table2.
The configuration also includes a rib-group statement, which is used to import routes from one routing table to another. A rib-group consists of an import-rib statement, which specifies the source routing table, and an export-rib statement, which specifies the destination routing table.
In this case, the rib-group name is inet-to-ispi, and the import-rib statement specifies inet.0 as the source routing table. The export-rib statement specifies ispi.inet.0 as the destination routing table.
This means that the routes from inet.0 will be imported into ispi.inet.0.
Therefore, the correct answer is B. The inet.0 route table will be imported into the ispi.inet.0 route table.
Reference:
1: Routing Instances Overview 2: Virtual Routing Instances : [rib-group (Routing Options)]
Question #3
What is the default keepalive time for BGP?
- A . 10 seconds
- B . 60 seconds
- C . 30 seconds
- D . 90 seconds
Correct Answer: B
B
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.
B
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.
Question #4
What is the maximum allowable MTU size for a default GRE tunnel without IPv4 traffic fragmentation?
- A . 1496 bytes
- B . 1480 bytes
- C . 1500 bytes
- D . 1476 bytes
Correct Answer: D
D
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.
D
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.
Question #5
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 updates the next-hop attribute to ensure reachability within an AS.
- B . IBGP peers advertise routes received from EBGP peers to other IBGP peers.
- C . IBGP peers advertise routes received from IBGP peers to other IBGP peers.
- D . EBGP peers advertise routes received from IBGP peers to other EBGP peers.
Correct Answer: BC
BC
Explanation:
In this scenario where you are a network operator wanting to add a second ISP connection and remove the default route to the existing ISP and decide to deploy the BGP protocol in the network, the correct two statements are:
IBGP peers advertise routes received from EBGP peers to other IBGP peers.
This is correct. Inside an Autonomous System (AS), IBGP peers will advertise routes learned from EBGP peers to other IBGP peers to ensure that all routers within the AS have information about external destinations.
IBGP peers advertise routes received from IBGP peers to other IBGP peers.
This is typically incorrect. Within IBGP, route information is not passed from one IBGP peer to another by default, to prevent routing information loops within an AS, unless route reflectors are configured or there is a full mesh IBGP setup.
BC
Explanation:
In this scenario where you are a network operator wanting to add a second ISP connection and remove the default route to the existing ISP and decide to deploy the BGP protocol in the network, the correct two statements are:
IBGP peers advertise routes received from EBGP peers to other IBGP peers.
This is correct. Inside an Autonomous System (AS), IBGP peers will advertise routes learned from EBGP peers to other IBGP peers to ensure that all routers within the AS have information about external destinations.
IBGP peers advertise routes received from IBGP peers to other IBGP peers.
This is typically incorrect. Within IBGP, route information is not passed from one IBGP peer to another by default, to prevent routing information loops within an AS, unless route reflectors are configured or there is a full mesh IBGP setup.
Question #6
Exhibit.
Which router will become the OSPF BDR if all routers are powered on at the same time?
- A . R4
- B . R1
- C . R3
- D . R2
Correct Answer: A
A
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.
Reference:
1: OSPF DR/BDR Election: Process, Configuration, and Tuning
2: OSPF Designated Router (DR) and Backup Designated Router (BDR)
A
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.
Reference:
1: OSPF DR/BDR Election: Process, Configuration, and Tuning
2: OSPF Designated Router (DR) and Backup Designated Router (BDR)