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

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Total 96 questions
Question 1

An interface is configured with a behavior aggregate classifier and a multifield classifier How will the packet be processed when received on this interface?



Answer : B

When a Juniper device receives a packet on an interface with both a Behavior Aggregate (BA) classifier and a Multifield (MF) classifier, Junos OS follows a specific processing order to apply Class of Service (CoS).

Understanding the Classifiers in Junos CoS

1 Behavior Aggregate (BA) Classifier

Uses packet headers (DSCP, IP precedence, or MPLS EXP bits) to classify traffic into forwarding classes.

Applied at the ingress interface.

Example: A packet with DSCP 46 (Expedited Forwarding) is mapped to a high-priority queue.

2 Multifield (MF) Classifier

Uses match conditions (like source/destination IP, port numbers, protocol types) to classify traffic.

Typically used for more granular classification beyond what BA can provide.

Junos Processing Order:

When both BA and MF classifiers are configured on an interface, Junos first applies the BA classifier, then the MF classifier. MF classifier can override the BA classification if necessary.

Evaluating the Answer Choices

B. The packet will be processed by the BA classifier first, then the MF classifier.

Correct, because Junos first applies BA classification based on DSCP/MPLS EXP bits.

After BA classification, the MF classifier is applied, which can refine or override the BA classification.

A. The packet will be discarded.

Incorrect, because classification does not drop packets unless explicitly configured with a filter or policing action.

C. The packet will be forwarded with no classification changes.

Incorrect, because both classifiers are applied in a specific order, meaning classification changes will occur.

D. The packet will be processed by the MF classifier first, then the BA classifier.

Incorrect, because BA classification is always applied first, followed by MF classification.

Final Answer: B. The packet will be processed by the BA classifier first, then the MF classifier.

Official Juniper Reference: 'When both BA and MF classifiers are applied on an interface, Junos OS first classifies packets using the BA classifier before applying the MF classifier.'


Question 2

Exhibit

You have MAC addresses moving in your EVPN environment

Referring to the exhibit, which two statements are correct about the sequence number? (Choose two)



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


Question 3

You have an L2VPN connecting two CEs across a provider network. The CEs and provider network are configured with the default MTU setting. You use the ping command from one

CE to the other CE with a size of 1500 bytes.

In this scenario, which statement is correct when using the ping command?



Answer : B

Layer 2 VPNs don't support fragmentation in the provider network. It is critical that the provider network supports the largest frame that the CE devices can generate after the MPLS and virtual routing and forwarding (VRF) labels are added by the PE devices. This example leaves the CE devices at the default 1500-byte maximum transmission unit (MTU) while configuring the provider core to support a 4000 byte MTU. This configuration avoids discards by ensuring the CE devices cannot exceed the MTU in the provider's network.


Question 4

After a recent power outage, your manager asks you to investigate ways to automatically reduce the impact caused by suboptimal routing in your OSPF and OSPFv3 network after devices reboot.

Which three configuration statements accomplish this task? (Choose three.)



Answer : A, C, E

To reduce the impact of suboptimal routing in OSPF and OSPFv3 after devices reboot, you can use the overload feature to prevent a router from being used as a transit router for a specified period of time. This allows the router to stabilize its routing table before forwarding traffic for other routers. To enable the overload feature, you need to do the following:

For OSPF, configure the overload statement under [edit protocols ospf] hierarchy level. You can also specify a timeout value in seconds to indicate how long the router should remain in overload state after it boots up. For example, set protocols ospf overload timeout 900 means that the router will be in overload state for 15 minutes after it boots up.

For OSPFv3, configure the overload statement under [edit protocols ospf3] hierarchy level. You can also specify a realm (ipv4-unicast or ipv6-unicast) and a timeout value in seconds to indicate how long the router should remain in overload state after it boots up for each realm. For example, set protocols ospf3 realm ipv4-unicast overload timeout 900 means that the router will be in overload state for 15 minutes after it boots up for IPv4 unicast routing.


Question 5

Exhibit.

Referring to the exhibit, what must be changed to establish a Level 1 adjacency between routers R1 and R2?



Answer : D


Question 6

Exhibit

R4 is directly connected to both RPs (R2 and R3) R4 is currently sending all ,o,ns upstream to R3 but you want all joins to go to R2 instead Referring to the exhibit, which configuration change will solve this issue?



Answer : D

The issue arises becauseR3's group-range (224.1.1.0/28)is more specific thanR2's group-range (224.1.1.0/24). In PIM bootstrap (BSR), the RP with thelongest prefix (most specific group-range)is preferred, regardless of priority. Even though R3 has a higher bootstrap priority (210 vs. R2's 200), its more specific/28group-range takes precedence for groups within224.1.1.0/28.

Why Option D is Correct:

To force R4 to useR2for all joins, R2's group-range must bemore specificthan R3's. For example:

If R2's group-range is changed to224.1.1.0/28(same as R3) but with ahigher priority, R2 would win (priority is compared only when group-ranges are equal).

If R2's group-range is changed to224.1.1.0/29(more specific than/28), it will override R3's/28for groups in the/29range.

The key isprefix specificity, which overrides priority in BSR elections.

Why Other Options Are Incorrect:

A . Change bootstrap priority on R2 to be higher than R3:

Priority is evaluatedonly when group-ranges are identical. Since R3's group-range (/28) is more specific than R2's (/24), R3 will still win for groups in224.1.1.0/28, even if R2's priority is higher.

B . Change the default route in inet.2 on R4:

RPF routes (inet.2) determine how traffic reaches the RP, but they do not influenceRP election logic(BSR priority/group-range).

C . Change R2's local address to be higher than R3's:

The RP address is a tiebreakeronly if priorities and group-ranges are equal. Since R3's group-range is more specific, this change has no impact.

Key Takeaways:

BSR RP Election Order:

Longest group prefix (most specific).

Highest priority(if prefixes are equal).

Highest RP address(if prefixes and priorities are equal).

To override R3, R2 must advertise amore specific group-range(e.g.,/28or smaller) to ensure it is selected for the desired multicast groups.

Reference: Juniper PIM Sparse Mode and BSR Configuration.


Question 7

Exhibit

Based on the configuration contents shown in the exhibit, which statement is true?



Answer : A

This configuration applies to IGMP (Internet Group Management Protocol) and is designed to control multicast group memberships on the interface ge-0/0/0.0.

Breaking Down the Configuration

1 Policy-Statement: block-igmp

policy-statement block-igmp {

term 1 {

from {

route-filter 224.7.7.7/32 exact;

source-address-filter 192.168.100.10/32 exact;

}

then reject;

}

}

This policy blocks IGMP joins for group 224.7.7.7 only if the source IP is 192.168.100.10.

If both conditions match, the request is rejected.

2 IGMP Configuration on Interface ge-0/0/0.0

[edit protocols igmp]

user@router# show

interface ge-0/0/0.0 {

group-policy block-igmp;

group-limit 25;

}

group-policy block-igmp applies the policy statement block-igmp, meaning IGMP join requests are evaluated based on this policy.

group-limit 25 means the interface allows up to 25 multicast groups.

Evaluating the Answer Choices

A. Joins for group 224.7.7.7 are rejected if the source address is 192.168.100.10.

Correct, because:

The policy specifically matches group 224.7.7.7 and source IP 192.168.100.10.

If both conditions are met, the join is rejected.

B. Joins for any group are accepted if the group count value is less than 25.

Incorrect, because:

The group-limit (25) applies to the total number of IGMP groups but does not override explicit policy rules.

Even if there are fewer than 25 groups, a join request can still be rejected by the policy statement.

C. Joins for group 224.7.7.7 are always rejected, regardless of the group count.

Incorrect, because:

The policy only blocks joins from the specific source 192.168.100.10.

Joins from other sources to 224.7.7.7 are allowed.

D. Joins for group 224.7.7.7 are accepted if the group count is less than 25.

Incorrect, because:

Joins for 224.7.7.7 from source 192.168.100.10 will always be rejected, even if the group count is below 25.

The group-limit does not override the rejection policy.

'Joins for group 224.7.7.7 are rejected if the source address is 192.168.100.10.'

Official Juniper Documentation Reference: Junos IGMP Policy Configuration Guide

'A group-policy statement allows filtering IGMP joins based on multicast group address and source IP.'


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