Juniper JN0-351 Practice Test - Questions Answers, Page 4

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.

The exhibit shows the output of the commandshow ospf neighbor, which displays information about the OSPF neighbors on a router1.

The output shows that the OSPF neighbor with the address 172.26.1.1 and the interface ge-0/0/3.0 is in the Exstart state1.

The Exstart state is the fourth state in the OSPF neighbor formation process, after Down, Init, and 2-Way states2.In this state, the OSPF neighbors establish a master-slave relationship and exchange database description (DBD) packets, which contain summaries of their link-state databases2.

The most common reason for OSPF neighbors to be stuck in the Exstart state is an MTU mismatch between the interfaces3.MTU stands for maximum transmission unit, which is the largest size of a packet that can be transmitted on a network segment4.If the MTU values of two OSPF neighbors are different, they may not be able to exchange DBD packets successfully, as some packets may be dropped or fragmented due to their size exceeding the MTU limit3.

To solve this problem, you need to ensure that the MTU values of both OSPF neighbors are the same or compatible.You can use the commandshow interfacesto display the MTU value of an interface5. You can also use the commandpingwith thedo-not-fragmentoption to test the MTU size between two routers.You can change the MTU value of an interface by using the commandset interfaces interface-name mtu mtu-valuein configuration mode5.

IS-IS (Intermediate System to Intermediate System) is a routing protocol that is designed to move information efficiently within a computer network12.It supports multiple protocol topologies, including IPv4, IPv6, and multicast12. Therefore, options C, E, and D are correct.

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.

Ais 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 snooping1.DAI discards any ARP packets that do not match the database or have invalid formats1.

Cis 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 ports2.DHCP snooping also builds a database of MAC addresses, IP addresses, lease times, and binding types for each client2.

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.

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.