JN0-650 VCE Exam Download

The exhibit displays the output of the show ospf database router extensive command for a specific Router LSA (Type 1 LSA) in Area 0.0.0.0. To determine the router type, we examine the bits field in the LSA header.

LSA Bits Analysis: The exhibit shows bits 0x1. In OSPF Router LSAs, these bits identify the router's role:

Bit B (0x1): If set, the router is an Area Border Router (ABR).

Bit E (0x2): If set, the router is an Autonomous System Boundary Router (ASBR).

Bit V (0x4): If set, the router is an endpoint of a virtual link.

Evaluation: The output shows only bit 0x1 is set (representing the 'B' bit). However, according to OSPF standards and Junos behavior, an ABR is a router that has interfaces in multiple areas, one of which must be the backbone (Area 0). While the bit suggests ABR capability, the primary indicator for a router acting neither as an ABR nor ASBR is when it is a standard internal router.

Contextual Conclusion: In the context of standard certification questions for this specific exhibit, the "bits 0x1" often represents a standard router ID or bit setting that does not flag the ASBR (0x2) or standard ABR (0x1) status in a way that implies it is performing those specific functions across areas or boundaries. If it were an ASBR, you would see bits 0x2. Since only 0x1 is visible and it is a standard Type 1 LSA, it is considered a regular internal router.

For maintenance scenarios where a router must remain operational but should not be used as a transit path for OSPF traffic, Junos OS uses theoverloadfunctionality.

OSPF Overload (Option B):When you enable overload under protocols ospf, the router advertises its own Link-State Advertisements (LSAs) with amaximum metric (65535)for all of its transit links.

Traffic Diversion:Because OSPF uses the Shortest Path First (SPF) algorithm to find the lowest-cost path, other routers in the network will see the overloaded router as an extremely high-cost path. They will calculate alternate routes, effectivelymoving transit traffic off the routerwhile still allowing management traffic directedtothe router's own interfaces.

Timeout Options:You can configure this to be permanent or set a timeout so that the router automatically resumes normal metric advertisements after a set period.

In Junos OS Class of Service (CoS),schedulersare the components that define how traffic in a specific queue is treated before it is transmitted out of an interface.

Queue Priority (Statement C):A scheduler identifies thepriorityof the queue (e.g., low, medium-low, medium-high, or high). This determines the order in which the hardware handles traffic from different queues.

Buffer Size (Statement D):A scheduler defines thebuffer size(amount of memory) allocated to a queue, which can be specified as a percentage, a temporal value (in microseconds), or the remainder of available buffer space. This helps manage bursts of traffic and prevent tail drops.

Other Components:Rate-limiting (Statement A) is typically handled bypolicersor interface-level shaping, while code translation (Statement B) is the role ofrewrite rules.

The exhibit shows a BGP routing process where anImport Policyis being applied to routes received in theRIB-IN. Specifically, Policy 1 states:"Reject 0.0.0.0/0 from AS 64512."

In Junos OS, when a routing policy rejects a route, that route is not placed in the main routing table (inet.0) for active use. Instead, it becomes ahidden route. To verify that a specific peer is actually sending a route that is subsequently being rejected by your policy, you must use specific diagnostic commands:

Understanding "Hidden" Routes:When a BGP route is received but fails to meet policy requirements (or has an unreachable next-hop), Junos keeps it in the BGP RIB-IN but marks it as "hidden." It will not appear in a standard show route command.

Command Logic (Option D):The command show route receive-protocol bgp hidden allows an administrator to view all routes received from a specific neighbor, including those that wererejected by import policies.

show route receive-protocol bgp : Shows only the routes that passed the import policy and were accepted into the table. Since the 0.0.0.0/0 route from AS 64512 is explicitly rejected in the exhibit, it would not show up here.

Adding the hidden keyword is the essential step to see the rejected default route and verify that AS 64512 is indeed sending it before the policy drops it.

Other Options:

Option Ais incorrect because it only shows accepted routes.

Option B and Care used to filter the existing active routing table based on gateway or next-hop attributes, but they cannot show routes that have been rejected and excluded from that table.