Important Juniper JN0-650 JNCIP-ENT Exam Questions

Answer: A, C, E

Explanation:

In Junos OS, the figure-of-merit is an internal numerical value used by the BGP Route Damping mechanism to quantify the stability of a specific BGP route. When a route 'flaps' (becomes unstable), the Junos OS increases this value by assigning a specific penalty based on the type of event that occurred:

The route is withdrawn (Option A): When a BGP neighbor sends a withdrawal message for a prefix, Junos assigns a significant penalty---typically 1,000 by default---to the route's figure-of-merit.

The route is readvertised (Option C): When a previously withdrawn route is announced again by the neighbor, the Junos OS adds another penalty to the figure-of-merit value to track the continued instability.

The route's path attributes changed (Option E): If a route remains reachable but its BGP attributes (such as the AS Path or Community) change, it is considered a flap. Junos assigns a smaller penalty---typically 500 by default---for this attribute change.

As the figure-of-merit accumulates and exceeds a predefined suppress threshold, the route is suppressed and no longer used for forwarding. Over time, the value decreases according to a configured half-life until it falls below a reuse threshold, at which point the route becomes active again. Factors like local preference or the origin (IBGP/EBGP) do not trigger these internal penalty increments for the figure-of-merit.

Answer: B, D

Explanation:

When 802.1X server fail fallback is enabled with the vlan-name feature, the switch provides a specific survival mechanism for both existing and new sessions when the RADIUS server becomes unreachable.

Existing Clients (Statement B): Clients that have already successfully authenticated are unaffected by the server's unavailability in the short term. They maintain their current network access until their specific re-authentication timer expires. Only then will the switch attempt to contact the server again and trigger the fallback action if the server remains down.

New Clients (Statement D): For any new device attempting to connect while the RADIUS server is down, the switch cannot perform a standard authentication. Under the vlan-name fallback configuration, these new clients are automatically placed into the specified fallback VLAN and granted access based on the local policy defined for that VLAN.

Why others are incorrect: Statement A is incorrect because disconnecting active users would cause unnecessary service disruption. Statement C is incorrect because new clients cannot 'request' a VLAN during the 802.1X handshake; the switch assigns it based on the fallback configuration.

Answer: A, C

Explanation:

In Junos OS Class of Service (CoS), a scheduler is the mechanism used to assign resources to the various egress queues on an interface. Specifically, when utilizing a modified deficit round-robin (MDRR) or weighted round-robin algorithm to service these queues, the scheduler's behavior is defined by two primary variables:

Transmit Rate (Option A): This variable defines the minimum guaranteed bandwidth for a queue. In the context of a deficit round-robin algorithm, the transmit rate serves as the weight for the queue. Queues with higher transmit rates receive a larger 'quantum' of data they can send during each round-robin cycle compared to queues with lower rates.

Buffer Size (Option C): This variable defines the amount of memory (buffer space) allocated to the queue. It ensures that the queue can hold a certain amount of delayed traffic during periods of congestion to prevent immediate packet drops. The buffer size can be configured as a percentage of the total interface buffer or as a temporal value.

Why other options are incorrect:

Layer 2 and Layer 3 fields (Options B & D): These fields are utilized by classifiers (Behavior Aggregate or Multifield) to identify and group traffic into forwarding classes. They are used before the scheduling process begins and do not define the resource allocation of the scheduler itself.

Answer: D

Explanation:

The behavior described is the fundamental operational principle of OSPF's hierarchical area structure.

LSA Flooding Scope: In OSPFv2, Type-1 (Router) and Type-2 (Network) Link-State Advertisements (LSAs) are restricted to a local area flooding scope. They contain detailed topology information (such as which routers are connected to which links) that is only relevant for calculating the Shortest Path First (SPF) tree within that specific area.

ABR Functionality: Area Border Routers (ABRs), such as R1 in this scenario, act as the gateway between areas. The ABR does not forward Type-1 or Type-2 LSAs from one area to another. Instead, it extracts the prefix information (the network address and mask) from those LSAs and generates a Type-3 (Summary) LSA.

Interarea Reachability: This Type-3 LSA is then flooded into the backbone (Area 0) and subsequently into other non-backbone areas, such as Area 2. This explains why R2 sees an 'interarea route' to R3's network in its routing table and has the corresponding Type-3 LSA in its database, but cannot see the original Type-1 or Type-2 LSAs from Area 1.

Why other options are incorrect: Option A is incorrect because this is standard protocol behavior, not the result of a manual filter. Option B is incorrect as there is no such 'disable' feature; the protocol design inherently prevents these LSAs from crossing boundaries. Option C is incorrect because OSPFv3 still uses Type-1 and Type-2 LSAs (renamed but functionally similar for topology), and the prompt specifically identifies the deployment as OSPFv2.

Answer: B, D

Explanation:

The exhibit illustrates a standard end-to-end Class of Service (CoS) path consisting of an edge router (R1) and core/intermediate routers (R2 and R3).

Edge Classification (Option B): The scenario specifies that video traffic enters the network without any class-of-service markings. Because there are no DSCP or 802.1p bits to inspect, the ingress router (R1) cannot use simple Behavior Aggregate (BA) classification. Instead, it must use Multifield (MF) classification. MF classification allows the router to look deeper into the packet (Source/Destination IP, Protocol, Port numbers) to identify the video stream and assign it to a specific forwarding class. * Core Classification (Option D): Once R1 has identified the traffic, it will typically apply a rewrite rule on its egress interface to mark the packets with a specific CoS value (like a DSCP code). Consequently, the downstream routers (R2 and R3) do not need to perform expensive deep-packet inspection again. They can use Behavior Aggregate (BA) classification, which simply looks at the markings in the packet header to determine the appropriate forwarding priority.

Option A and C: These are incorrect because BA classification is impossible on unmarked ingress traffic, and performing MF classification in the core is inefficient and not a recommended Juniper design practice for high-speed transit.