Juniper JN0-664 Service Provider Routing and Switching, Professional Exam JNCIP-SP Exam Practice Test

Answer : A

The exhibit shows the configuration of a VRF (Virtual Routing and Forwarding) instance on a Juniper PE router. Let's break down the key components:

VRF Configuration (VPN-A)

The instance type is VRF, meaning this is an L3VPN (Layer 3 VPN).

The routing instance contains a static route (10.1.0.0/16 next-hop 10.1.0.1).

The interface ge-0/0/2.0 is assigned to the VRF.

Route Distinguisher (RD): 172.17.20.1:1

VRF-Export Policy: vpn-a-export

VRF-Target: target:65512:1 (This defines which routes will be imported into the VRF).

VRF Export Policy (vpn-a-export)

The vpn-a-export policy adds two BGP communities (route targets) to exported VPN routes:

community add vpn-a-target;

community add vpn-m-target;

accept;

The vpn-a-target community corresponds to target:65512:1.

The vpn-m-target community corresponds to target:65512:2.

Policy-Options (Community Definitions)

community vpn-a-target members target:65512:1;

community vpn-m-target members target:65512:2;

This confirms that routes exported from this VRF will have BOTH target:65512:1 and target:65512:2.

Evaluating the Answer Choices

Option A: 'VPN routes are exported with the target:65512:1 and target:65512:2 route targets.'

The vpn-a-export policy explicitly adds both vpn-a-target (65512:1) and vpn-m-target (65512:2) to exported routes.

This is correct.

Option B: 'You cannot use the vrf-target and vrf-export statements in the same VRF.'

This is incorrect.

Juniper allows the use of both vrf-target and vrf-export in the same VRF:

vrf-target is used for importing routes.

vrf-export defines export policies (which can add additional route targets).

This is incorrect.

Option C: 'VPN routes with the target:65512:1 and target:65512:2 route targets are imported.'

The vrf-target target:65512:1; statement only controls importing routes.

The import policy does not include target:65512:2, so routes tagged with target:65512:2 alone would not be imported into this VRF.

This is incorrect.

Option D: 'VPN routes are exported with only the target:65512:1 route target.'

The export policy (vpn-a-export) clearly adds both 65512:1 and 65512:2.

This is incorrect.

Final Answer:

A. VPN routes are exported with the target:65512:1 and target:65512:2 route targets.

Verification from Juniper Documentation

Juniper MPLS L3VPN Configuration Guide confirms that vrf-target is used for importing, while vrf-export can be used for exporting multiple route targets.

Juniper Routing Policy Documentation states that export policies can add multiple BGP communities (route targets).

RFC 4364 (BGP/MPLS IP VPNs) defines the use of route targets for VPN route control.

Answer : D

When configuring Class of Service (CoS) properties for output queues, we need to manage packet drops during periods of congestion. Juniper's CoS framework provides several tools to manage congestion, including drop profiles, buffer sizes, and scheduling mechanisms. Let's break down each option and identify the correct one.

Evaluating the Answer Choices

D. drop profile (Correct Answer)

Why?

A drop profile defines when packets should be dropped based on the queue fill level.

Random Early Detection (RED) or Tail Drop can be used to manage congestion by discarding lower-priority packets first.

Drop profiles are configured under the scheduler to determine how aggressive packet dropping should be during congestion.

Example Juniper Configuration:

schedulers {

best-effort {

drop-profile low-drop;

}

}

drop-profiles {

low-drop {

fill-level 80 drop-probability 50;

}

}

fill-level 80 When the queue reaches 80% full, packet drops begin.

drop-probability 50 There is a 50% chance of dropping packets once the threshold is reached.

Official Juniper Documentation Reference: Junos Class of Service Configuration Guide

'A drop profile determines how packets are discarded based on the queue fill level, allowing control over congestion behavior.'

Why the Other Options Are Incorrect?

A. buffer size (Incorrect)

Why?

The buffer size determines how many packets the queue can store before congestion occurs.

A larger buffer can delay drops, but it does not actively control dropping behavior.

It affects latency rather than controlling packet drops.

B. priority (Incorrect)

Why?

Priority controls which queue gets serviced first, not how drops are handled.

Higher priority queues are serviced before lower-priority queues, but this does not prevent congestion-related drops.

C. shaping rate (Incorrect)

Why?

Shaping limits the maximum transmission rate of the queue.

While shaping helps reduce congestion, it does not control which packets get dropped during congestion.

Shaping is useful for traffic smoothing, but it does not actively drop packets based on queue fill levels.

Final Answer: D. drop profile

Controls packet drops based on queue congestion.

Defines RED (Random Early Detection) or Tail Drop mechanisms.

Directly influences drop probability as the queue fills up.

Official Juniper Reference: 'Drop profiles are used to manage congestion by determining when and how aggressively packets are dropped based on queue fill level.'

Answer : C, D, E

Answer : D

The attached bit is a flag in an IS-IS LSP that indicates whether a router is connected to another area or level (L2) of the network. By default, L2 routers set this bit when they advertise their LSPs to L1 routers, and L1 routers use this bit to select a default route to reach other areas or levels through L2 routers. However, this may result in suboptimal routing if there are multiple L2 routers with different paths to other areas or levels. To ensure that L1 routers have only the most specific routes available from L2 routers, you can configure the ignore-attached-bit parameter on all L1 routers. This makes L1 routers ignore the attached bit and install all interarea routes learned from L2 routers in their routing tables.

Answer : B, D, E

Junos platforms use different mechanisms to evaluate incoming traffic for CoS purposes, such as:

Behavior aggregate classifiers: These classifiers use a single field in a packet header to classify traffic into different forwarding classes and loss priorities based on predefined or user-defined values.

Fixed classifiers: These classifiers use a fixed field in a packet header to classify traffic into different forwarding classes and loss priorities based on predefined values.

Multifield classifiers: These classifiers use multiple fields in a packet header to classify traffic into different forwarding classes and loss priorities based on user-defined values and filters.

Rewrite rules and traffic shapers are not used to evaluate incoming traffic for CoS purposes, but rather to modify or shape outgoing traffic based on CoS policies.

Answer : C

OSPF uses different types of LSAs to describe different aspects of the network topology. Type 1 LSAs are also known as router LSAs, and they describe the links and interfaces of a router within an area. Type 3 LSAs are also known as summary LSAs, and they describe routes to networks outside an area but within the same autonomous system (AS). By default, OSPF will summarize routes from Type 1 LSAs into Type 3 LSAs when advertising them across area boundaries .

Answer : C, D

In an EVPN (Ethernet Virtual Private Network) environment, MAC address mobility is a critical feature that allows devices to move across different locations while ensuring the network consistently tracks their MAC addresses. Let's break down the components in the exhibit and analyze the correct statements.

Understanding MAC Mobility and Sequence Numbers in EVPN

In EVPN, MAC mobility is managed through sequence numbers that are included in Type 2 MAC/IP advertisements.

The sequence number tracks MAC movement events and is used to determine the most recent update when a MAC address appears on different PEs (Provider Edge devices).

When a MAC address moves between locations, the EVPN PEs increment the sequence number and advertise it to resolve conflicts and determine which PE has the most up-to-date information.

Now, Let's Review the Options:

C. It helps the local PE to identify the latest advertisement.

Correct: The sequence number plays a key role in resolving MAC address conflicts. If multiple PEs advertise the same MAC address, the PE compares the sequence numbers to determine which update is the latest.

A higher sequence number indicates a more recent MAC update.

D. It is advertised using a Type 2 message.

Correct: EVPN MAC/IP advertisements use BGP EVPN Type 2 messages to carry MAC addresses, IP addresses (optional), and their associated sequence numbers.

Type 2 advertisements are used to track MAC mobility and IP reachability information in the EVPN.

Why the Other Options Are Incorrect:

A. It identifies MAC addresses that should be discarded.

Incorrect: The sequence number doesn't identify MAC addresses that need to be discarded. Instead, it resolves conflicts by determining the most recent MAC address advertisement based on the highest sequence number.

B. It resolves conflicting MAC address ownership claims.

Partially true, but misleading: While it's true that sequence numbers are used in conflict resolution, the sequence number itself doesn't directly resolve ownership claims. It only helps determine which advertisement is more recent. The actual conflict resolution happens through the comparison of the advertisements and sequence numbers.

Final Answer:

C. It helps the local PE to identify the latest advertisement. D. It is advertised using a Type 2 message.

Reference from Juniper Documentation:

Juniper EVPN Configuration Guide:

'In EVPN MAC/IP advertisements, sequence numbers track the mobility of MAC addresses and are used to resolve conflicts when the same MAC address is advertised by multiple PEs. The PE with the higher sequence number has the most recent information.' Juniper BGP EVPN Mobility Documentation