JN0-351 Exam Dumps : Enterprise Routing and Switching Specialist (JNCIS-ENT)

BGP (Border Gateway Protocol) is a protocol designed to exchange routing and reachability information among autonomous systems (AS) on the internet1.

• Option A is correct. When an EBGP router advertises routes to its neighbors, it appends its AS number to the AS_PATH attribute1. This is a key mechanism in BGP to prevent routing loops1.
• Option C is correct. BGP has a built-in loop prevention mechanism whereby if a BGP router detects its own AS in the AS_PATH attribute, it will drop the prefix and will not continue to advertise it2. This helps to prevent routing loops2.
• Option B is incorrect. EBGP routers do not accept routes that contain their own AS number in the AS_PATH2. Instead, they drop such routes as part of the loop prevention mechanism2.
• Option D is incorrect. While it’s true that EBGP routers append their AS number when advertising routes, they do not prepend their AS number1. The term “prepend” in BGP usually refers to a technique used to influence path selection by artificially lengthening the AS_PATH3.

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.

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.