Free JN0-351 Exam Dumps Preview

Explanation: On Juniper switches, the default VLAN is set to a VLAN ID of 1 by default 12. 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 changed 12. This allows network administrators to configure the switch to use a different VLAN as the default, if necessary 12. Therefore,
option D is correct.

Explanation: The output shown in the exhibit is the result of the command "show ip bgp neighbor 10.36.1.4 received-routes", which displays all received routes (both accepted and rejected) from the specified neighbor.
Option A is correct, because the routes displayed have traversed one or more autonomous systems. This can be seen from the AS_PATH attribute, which shows the sequence of AS numbers that the route has passed through. For example, the route 10.0.0.0/8 has an AS_PATH of 65001 65002, which means that it has traversed AS 65001 and AS 65002 before reaching the local router.
Option B is correct, because the output shows routes that were received prior to the application of any BGP import policies. This can be seen from the fact that some routes have a status code of "r", which means that they are rejected by an import policy. The"received-routes" keyword shows the routes coming from a given neighbor before the inbound policy has been applied. To see the routes after the inbound policy has been applied, the "routes" keyword should be used instead.
Option C is incorrect, because the output does not show routes that are active and rejected by an import policy. The status code of "r" means that the route is rejected by an import policy, but it does not mean that it is active. The status code of ">"
means that the route is active and selected as the best path. None of the routes in the output have both ">" and "r" status codes.
Option D is incorrect, because the routes displayed are not being learned from an IBGP peer. An IBGP peer is a BGP neighbor that belongs to the same AS as the local router. The output shows that the neighbor 10.36.1.4 has a remote AS of 65001, which is different from the local AS of 65002. Therefore, the neighbor is an EBGP peer, not an IBGP peer.

Explanation: The DHCP snooping feature in Juniper Networks' EX Series switches works by building a binding database that maps the IP address, MAC address, lease time, binding type, VLAN number, and interface information 1. This database is used to filter and validate DHCP messages from untrusted sources 1.
However, there are certain conditions that could prevent entries from being automatically created in the snooping database for an interface: MAC limiting: If MAC limiting is enabled on the interface, it could potentially interfere with the operation of DHCP snooping. MAC limiting restricts the number of MAC addresses that can be learned on a physical interface to prevent MAC flooding attacks 1. This could inadvertently limit the number of DHCP clients that can be learned on an interface, thus preventing new entries from being added to the DHCP snooping database.
Static IP address: If the device connected to the interface is configured with a static IP address, it will not go through the DHCP process and therefore will not have an entry in the DHCP snooping database 1. The DHCP snooping feature relies on monitoring DHCP messages to build its database1, so devices with static IP addresses that do not send DHCP messages will not have their information added.
Therefore, options B and C are correct. Options A and D are not correct because performing a DHCPRELEASE would simply remove an existing entry from the database1, and Dynamic ARP inspection (DAI) uses the information stored in the DHCP snooping binding database but does not prevent entries from being created 1.

Explanation: In this scenario, you should create an aggregate route 1. Aggregate routes are used for advertising summarized network prefixes 1. They help minimize the number of routing tables in an IP network by consolidating selected multiple routes into a single route advertisement 1. This approach is in contrast to non-aggregation routing, in which every routing table contains a unique entry for each route 1.
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 met 1. 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 neighbor 1.
Static route using qualified next hops: This type of route allows for the specification of multiple next-hop addresses for a static route 1. However, it does not provide the capability to summarize multiple routes into a single prefix.

Explanation:
https://www.juniper.net/documentation/en_US/junos/topics/concept/nsr-overview.html

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 commands 12. 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) instance 1. 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 traffic 1. 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 traffic 1.

Explanation: In Rapid Spanning Tree Protocol (RSTP), there are several port roles that determine the behavior of the port in the spanning tree 123. The roles include root, designated, alternate, backup, and disabled 123.
The discarding state is associated with the backup, alternate, and disabled roles 123. 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 state 2. Disabled ports are also in the discarding state 3.
Therefore, options B, C, and D are correct.

A is correct because dynamic ARP inspection (DAI) is a Layer 2 security feature that prevents ARP spoofing attacks. ARP spoofing is a technique that allows an attacker to send fake ARP messages to associate a spoofed MAC address with a legitimate IP address. This can result in traffic redirection, man-in-the-middle attacks, or denial-of-service attacks. DAI validates ARP packets by checking the source MAC address and IP address against a trusted database, which is usually built by DHCP snooping 1. DAI discards any ARP packets that do not match the database or have invalid formats 1.
C is correct because DHCP snooping is a Layer 2 security feature that prevents DHCP spoofing attacks.
DHCP spoofing is a technique that allows an attacker to act as a rogue DHCP server and offer fake IP addresses and other network parameters to unsuspecting clients. This can result in traffic redirection, man-in- the-middle attacks, or denial-of-service attacks. DHCP snooping filters DHCP messages by classifying switch ports as trusted or untrusted. Trusted ports are allowed to send and receive any DHCP messages, while untrusted ports are allowed to send only DHCP requests and receive only valid DHCP replies from trusted ports 2. DHCP snooping also builds a database of MAC addresses, IP addresses, lease times, and binding types for each client 2.

Explanation: In BGP, the path selection process is based on a set of attributes 1. 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 path 1.
Referring to the exhibit, all four ISPs have the same weight, local preference, and origin 1. However, ISP 4 has the shortest AS path 1. Therefore, ISP 4 will be selected as the active path. So, option C is correct.

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 device 1. A virtual-router routing instance allows administrators to divide a device into multiple independent virtual routers, each with its own routing table 2.
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)]

Explanation: BGP attributes are properties that BGP uses for route advertisement, path selection, and loop prevention 1. There are four categories of BGP attributes123: Well-known mandatory: Must be recognized by all BGP routers, present in all BGP updates, and passed on to other BGP routers 123.
Well-known discretionary: Supported by all BGP implementations, and are optionally included in BGP updates 1.
Optional transitive: May not be supported by all implementations of BGP1. Optional non-transitive: May not be supported by all implementations of BGP1. The well-known mandatory attributes must be supported by all BGP implementations and must be included in every update 123. These include the AS path and next hop attributes 23. Therefore, options A and C are correct.