JN0-649 Practice Exam Questions with Answers Enterprise Routing and Switching Professional (JNCIP-ENT) Certification

Understanding EVPN Route Types:

EVPN routes facilitate Layer 2 and Layer 3 connectivity across data centers.

Layer 2 and Layer 3 Connectivity:

For Layer 3 connectivity across data centers, where Layer 2 does not extend, IP prefixes need to be communicated.

Type 5 Routes:

Type 5 (IP Prefix Route):

Used to distribute IP prefixes between data centers.

Ensures that Layer 3 connectivity is established without extending Layer 2 domains.

References:

Juniper EVPN Type 5 Routes

Configuring EVPN for Data Center Interconnect

A modified deficit round-robin (MDRR) scheduler is defined by the following three variables:

Priority (A):

Priority determines the importance of the queue, influencing the order in which packets are serviced. Higher priority queues are serviced before lower priority queues.

Transmit rate (C):

The transmit rate controls the amount of bandwidth allocated to each queue. It determines how quickly packets from a queue can be transmitted.

Buffer size (E):

Buffer size defines the amount of memory allocated to each queue for storing packets before they are transmitted. Larger buffer sizes can accommodate more packets but may introduce more latency.

References:

Detailed information on MDRR and its variables can be found in Juniper's QoS configuration guides and related networking documents????.

Step 1: Check the error messages in the log.

The log messages indicate:

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Dec 22 19:22:29 router rpd[7394]: bgp_process_open:4185: NOTIFICATION sent to 192.168.1.4 (Internal AS 65000): code 2 (Open Message Error) subcode 2 (bad peer AS number), Reason: peer 192.168.1.4 (Internal AS 65000) claims 65100, 65000 configured

Dec 22 19:22:33 router rpd[7394]: bgp_pp_recv:4788: NOTIFICATION sent to 192.168.1.4+56714 (proto): code 2 (Open Message Error) subcode 2 (bad peer AS number), Reason: no group for 192.168.1.4+56714 (proto) from AS 65100 found (peer as mismatch) in master

Step 2: Interpret the messages.

The first message indicates that a BGP NOTIFICATION was sent to 192.168.1.4 due to an "Open Message Error" with a "bad peer AS number" because peer 192.168.1.4 claims AS 65100, but 65000 is configured.

The second message reiterates that the peer AS number 65100 does not match the configured AS 65000, causing a mismatch.

Step 3: Understand the MD5 key error.

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Dec 22 19:23:29 router kernel: tcp_auth_ok: Packet from 192.168.1.5:64047 missing MD5 digest

Dec 22 19:23:30 router kernel: tcp_auth_ok: Packet from 192.168.1.6:56201 missing MD5 digest

These lines indicate that packets from 192.168.1.5 and 192.168.1.6 are missing the MD5 digest, suggesting a potential MD5 key misconfiguration.

Step 4: Validate the answers.

Option B: The 192.168.1.5 peer has a misconfigured MD5 key. This is correct because the logs show that packets from 192.168.1.5 are missing the MD5 digest.

Option D: The 192.168.1.4 peer has a misconfigured autonomous system number. This is correct because the logs indicate that 192.168.1.4 claims AS 65100, while the router is configured for AS 65000.

References:

Document on useful Juniper commands for troubleshooting BGP and understanding log messages????.

Commands for checking BGP logs: show log messages | match notification, show bgp summary, show configuration protocols bgp????.

For devices like printers that do not support 802.1X authentication, you can configure static MAC bypass. This allows traffic from devices with specific MAC addresses to bypass 802.1X authentication and gain network access directly.

References:

From the Juniper documentation, you can implement static MAC bypass for devices that do not support 802.1X by configuring their MAC addresses to be statically permitted on the network.

Useful Juniper Commands.txt

Tech Ops Managed Router Juniper Install Guide

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# Example configuration for static MAC bypass

set protocols dot1x authenticator interface ge-0/0/1.0 mac-radius static-mac 00:11:22:33:44:55

commit

These configurations and explanations should address the questions accurately based on the provided information and referenced documents.

OSPF Protocol Basics:

OSPF (Open Shortest Path First) is a link-state routing protocol.

Routers exchange LSAs (Link-State Advertisements) to share topology information.

LSA Acknowledgment Mechanism:

OSPF uses a reliable mechanism to ensure LSAs are received.

When a router sends an LSA to a neighbor, it expects an acknowledgment (ACK).

If an ACK is not received within a certain period, the router will retransmit the LSA.

Acknowledgment Process:

LSAs are sent over OSPF's reliable transport, which ensures delivery through acknowledgments.

This mechanism helps to maintain consistent and up-to-date topology databases across routers.

References:

OSPF RFC 2328

Understanding OSPF Operations

Multitenancy with Routing Instances:

In a multitenant network, different tenants are isolated using routing instances.

Each routing instance can have its own routing table and policies.

BGP and Load Balancing:

BGP (Border Gateway Protocol) is often used for interconnecting different autonomous systems or for internal routing.

Load balancing in BGP can be achieved using the multipath feature, which allows the installation of multiple paths to the same destination in the routing table.

Additionally, configuring per-packet load balancing ensures that traffic is distributed across multiple paths more granularly.

Configuring Multipath in BGP:

Hierarchy Considerations: The multipath option must be configured at appropriate hierarchies to ensure it applies to the correct scope (either globally or within a specific routing instance).

Detailed Configuration:

Statement C: Configure a load-balance per-packet policy and apply it at the [edit routing-options forwarding-table] hierarchy.

Correct: Configuring a load-balance per-packet policy ensures that packets are distributed evenly across multiple paths. This is crucial for achieving effective load balancing.

Configuration Example:

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set routing-options forwarding-table export load-balance-per-packet

Policy Definition Example:

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set policy-options policy-statement load-balance-per-packet term 1 then load-balance per-packet

Statement D: Configure the multipath option at the [edit routing-instances routing-options] hierarchy.

Correct: Configuring multipath within a routing instance ensures that the load balancing feature is applied specifically to that instance, which is crucial in a multitenant environment.

Configuration Example:

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set routing-instances routing-options multipath

References:

Useful Juniper Commands

Juniper Routing Instances and Multipath Configuration

These configurations ensure that load balancing is achieved within each routing instance, leveraging both per-packet load balancing and the multipath feature in Junos OS for BGP. By configuring at the forwarding-table and routing-instance levels, you ensure the load balancing behavior is correctly applied to achieve the desired network performance and redundancy.

When MVRP is enabled, the protocol manages VLAN registration dynamically. In forbidden mode, VLANs are neither registered nor declared on the interface, meaning it prevents VLANs from being learned or propagated.

References:

Juniper Networks Configuration Guide on MVRP

Understanding the Problem:

The issue involves voice packets being dropped in a newly implemented VoIP network.

Voice packets are marked correctly for the expedited forwarding (EF) queue, indicating that classification is working as intended.

Dropped packets suggest that there may be insufficient resources allocated to handle the traffic in the EF queue.

Key Concepts:

Classifiers: These are used to mark packets so that they can be placed into the appropriate forwarding class. This step is already correctly implemented as indicated by the problem statement.

Rewrite Rules: These ensure that packets retain their markings as they transit the network, but this is not the issue here as packets are already marked correctly.

Policers: These control the rate of traffic to ensure it does not exceed specified limits, but policing is not required here as the issue is with packet drops due to insufficient resources.

Schedulers: These allocate resources (bandwidth, priority) to different queues to ensure that high-priority traffic (like VoIP) is transmitted with minimal delay and packet loss.

Solution: Configuring a Scheduler:

To prevent the EF queue from being starved of resources and to ensure voice packets are not dropped, you need to configure a scheduler. This scheduler will allocate appropriate bandwidth and priority to the EF queue.

Configuring Scheduler on Juniper Devices:

Here is a sample configuration to allocate bandwidth to the expedited forwarding queue:

set class-of-service schedulers voip-scheduler transmit-rate percent 20

set class-of-service schedulers voip-scheduler priority strict-high

set class-of-service forwarding-classes queue 1 expedited-forwarding

set class-of-service forwarding-classes queue 1 scheduler voip-scheduler

In this configuration:

The voip-scheduler is set to allocate 20% of the bandwidth and is given strict-high priority to ensure voice packets are transmitted with the highest priority.

The EF queue (queue 1) is associated with the voip-scheduler.

Verification:

Ensure the scheduler is applied and active on the interfaces handling the VoIP traffic.

Monitor the interface statistics to ensure that packet drops are minimized and voice quality issues are resolved.

References:

Juniper Networks Documentation on Class of Service

Configuring Schedulers

Understanding 802.1X Authentication:

802.1X is a network access control protocol that restricts access until the device or user is authenticated.

Guest VLAN Configuration:

When hosts fail authentication, they need to be placed in a separate VLAN to provide limited network access.

server-reject-vlan Command:

This command configures a VLAN for unauthenticated devices.

Ensures that devices that fail authentication are placed in a designated guest VLAN.

Configuration Example:

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set protocols dot1x authenticator interface ge-0/0/1.0 server-reject-vlan guest-vlan

References:

Juniper 802.1X Authentication Configuration Guide

Juniper Guest VLAN Configuration

When video packets are being dropped, and the network is configured to use the expedited-forwarding forwarding class, it typically indicates that the scheduler assigned to this class does not have sufficient bandwidth to handle the traffic. Adjusting the scheduler to allocate more bandwidth to the expedited-forwarding class will ensure that video packets are transmitted without being dropped.

Steps:

Identify the scheduler map: First, identify the scheduler map that is applied to the interfaces. This can be done using the following command:

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show configuration class-of-service scheduler-maps

Adjust the scheduler: Modify the scheduler for the expedited-forwarding forwarding class to support a higher transmit rate. You can edit the scheduler configuration to increase the bandwidth allocated.

Example:

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set class-of-service schedulers expedited-forwarding transmit-rate percent 30

Apply the configuration: Apply the modified scheduler to the interfaces using the following commands:

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set class-of-service interfaces ge-0/0/0 scheduler-map

set class-of-service interfaces ge-0/0/1 scheduler-map

commit

References:

Useful Juniper Commands.txt

Tech Ops Managed Router Juniper Install Guide

Step 1: Identify the requirements for interface-level authentication.

Ensure only corporate devices can connect using their MAC addresses.

Centralized server handles authentication.

Step 2: Evaluate authentication methods.

MAC RADIUS: Uses MAC addresses for authentication via a centralized RADIUS server.

Captive Portal: Typically used for guest access, not suitable for restricting to corporate devices.

802.1X with single-secure supplicant mode: Ensures only one device per port, but requires certificates or credentials, not just MAC addresses.

802.1X with multiple supplicant mode: Allows multiple devices per port, still requires certificates or credentials.

Step 3: Select the appropriate method.

MAC RADIUS: Satisfies the requirement of using MAC addresses for device authentication via a centralized server.

References:

Juniper authentication configuration and best practices????.

Commands for configuring MAC RADIUS: set protocols dot1x authenticator interface mac-radius, set access radius-server ????.