JN0-649 Juniper Enterprise Routing and Switching Professional (JNCIP-ENT) Free Practice Exam Questions (2025 Updated)

To troubleshoot why ISP peers are not receiving any routes in a multihomed BGP setup, the following steps are essential:

Verify Active BGP Routes: Ensure that the BGP routes are active in the routing table. Only active routes can be advertised to BGP peers.

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show route protocol bgp

Verify Export Policies: Check the export policies configured on your router. The export policies determine which routes are advertised to BGP peers. If these policies are incorrectly configured or missing, routes will not be advertised.

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show configuration policy-options policy-statement

show configuration protocols bgp group export

References:

Useful Juniper Commands.txt

Tech Ops Managed Router Juniper Install Guide

In a PIM-SM (Protocol Independent Multicast - Sparse Mode) network setup:

Before the formation of the rendezvous-point tree, a join message is sent from R1 to R3 (RP):

R1, being the router connected to the receiver, sends a PIM join message towards the RP (R3) to join the multicast group.

Before the formation of the rendezvous-point tree, an IGMP is sent from the Receiver to R1:

The receiver sends an IGMP membership report to its directly connected router (R1), indicating its interest in joining a multicast group.

References:

The behavior of PIM-SM and the process of join messages and IGMP reports are covered in multicast networking sections of network configuration and design guides​​​​.

In the given scenario, the connection between DC1 and DC2 is routed through a Layer 3 network. This indicates that the devices connecting the two data centers must be capable of performing Layer 3 routing to ensure that traffic can be properly forwarded across the network. Additionally, the use of VXLAN suggests that Integrated Routing and Bridging (IRB) functionality is required to enable communication between Layer 2 networks over the Layer 3 infrastructure.

The border devices (QFX10002) must handle Layer 3 routing to manage IP traffic between the data centers.

IRB functionality is necessary for routing between VLANs, allowing VXLAN to carry Layer 2 traffic across the Layer 3 network.

References:

The diagrams indicate the use of VXLAN for Layer 2 extension over a Layer 3 network.

The need for IRB is suggested by the presence of routed interfaces (IRB1 and IRB2) in the data center diagrams.

The "Tech Ops Managed Router Juniper Install Guide" provides insights into the Layer 3 routing capabilities and configurations necessary for such setups​​​​.

 OSPF Route Summarization Benefits:

Reduces Routing Table Size: By summarizing routes, multiple specific routes are combined into a single route. This reduces the number of entries in the routing table, making it more efficient and easier for the devices to process. This is critical in large networks to maintain performance and manageability.

Reduces Impact of Topology Changes: When a topology change occurs in one of the summarized routes, it does not need to propagate throughout the entire network. Only the summary route may need to be updated, which minimizes the impact and limits the scope of updates needed.

 Implementation in OSPF:

Configuration Example:

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set protocols ospf area 0.0.0.0 range 10.1.0.0/16

This command summarizes the routes in area 0.0.0.0 to a single route of 10.1.0.0/16.

 References:

The documents provided, such as "network-mgmt.pdf" and other relevant configuration guides, emphasize these benefits as fundamental to efficient OSPF deployment​​​​.

Understanding IEEE 802.3af Standard:

IEEE 802.3af, also known as PoE (Power over Ethernet), specifies the standard for delivering power over Ethernet cables.

This standard allows devices like IP phones to receive power along with data over the same cable.

Maximum Power Allocation:

According to the IEEE 802.3af standard, the maximum power that can be delivered to a powered device is 15.4 watts.

This power is delivered over Category 5 (Cat 5) cables or higher.

EX Series Switches Compliance:

Juniper EX Series switches with PoE support adhere to the IEEE 802.3af standard.

Thus, each PoE port on these switches can allocate up to 15.4 watts to connected devices.

References:

IEEE 802.3af standard specifications

Juniper EX Series switch documentation

Area-1 has no external connections. However, Area-1 has static route (172.16.31.0/24) that are not internal OSPF route. You can limit the external route advertisements to the area and advertise the static routes by designating the area an NSSA. In an NSSA, the ASBR (vMX1) generates NSSA external (Type 7) LSAs and floods them into the NSSA, where they are contained. Type-7 LSAs allow an NSSA to support the presence of ASBR and their corresponding external routing information. The ABR (vMX2) converts Type-7 LSAs into Type-5 External LSAs and leaks them to the other areas, but external routes from other areas are not advertised within the NSSA. An admin should check this and change it https://www.packetswitch.co.uk/configuring-junos-ospf-stub-and-nssa-areas/ https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/ref/statement/nssa-edit-protocols-ospf.html

When two BGP routes have identical attributes (MED, origin, AS path length, local preference), BGP uses the router ID as a tie-breaker. In this case, route 2 has a higher router ID (10.10.200.1 vs. 10.10.100.1). BGP will select the route with the higher router ID as the active route.

References:

Useful Juniper Commands.txt

Tech Ops Managed Router Juniper Install Guide

Analyzing BGP Route Information:

The exhibit shows BGP route information for the prefix 203.0.113.0/24.

Both paths to this prefix are learned from the same BGP peer with IP address 192.168.10.36.

Understanding BGP Neighbors:

The presence of multiple paths for the same prefix does not necessarily indicate multiple neighbors.

In this case, the routes to 203.0.113.0/24 are both learned from a single neighbor (192.168.10.36), but via different interfaces (ae8.0 and ae7.0).

Conclusion:

The BGP routes in the exhibit indicate that the prefix is learned from one neighbor but via different interfaces.

References:

BGP route analysis

Understanding BGP multi-path and neighbor relationships

From the provided IS-IS adjacency outputs:

R1 is configured to participate in both Level 1 and Level 2 (A): This is indicated by the adjacency states for both Level 1 and Level 2 on the R1 interfaces.

R2 is configured to participate in Level 2 only (D): This is shown by the adjacency state for Level 2 only on the R2 interfaces.

References:

The IS-IS adjacency outputs indicate the state and levels of participation for each router.

Configuration and command references from "Example configs for VMRCAXP01W.txt" and other documents provide context for understanding IS-IS states and levels​​​​​​.

Enabling LLDP-MED:

LLDP-MED (Link Layer Discovery Protocol - Media Endpoint Discovery) is an extension of LLDP specifically for VoIP devices.

It allows network devices to advertise and receive configuration information, such as VLAN IDs, from the network switch.

Voice VLAN Feature:

The voice VLAN feature on switches is designed to simplify the deployment of VoIP by automatically placing voice traffic on a designated VLAN.

Configuring the appropriate access interfaces and VLAN ID for voice traffic ensures that voice packets are prioritized and properly segmented from other types of traffic.

Configuration Steps:

Enable LLDP-MED on the appropriate access interfaces:

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set protocols lldp-med interface ge-0/0/0

Enable the voice VLAN feature and specify the VLAN ID:

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set ethernet-switching-options voip interface ge-0/0/0 vlan voice

set ethernet-switching-options voip interface ge-0/0/0 forwarding-class assured-forwarding

References:

Juniper documentation on LLDP-MED

Juniper EX Series switch configuration guide for voice VLAN

For Multiple Spanning Tree Protocol (MSTP) to operate correctly, all switches in the same region must have the same VLAN to instance mapping, revision level, and configuration name. These parameters ensure that all switches interpret the MSTP configuration consistently.

References:

MSTP Configuration Guide, Juniper Networks

Understanding the Problem:

The requirement is to provide Layer 2 connectivity between campus sites using Ethernet switches through a metro Ethernet service provider who is using Q-in-Q tagging.

Design Considerations:

VXLAN Implementation:

VXLAN (Virtual Extensible LAN) can be used to extend Layer 2 networks over Layer 3 networks. It is often used to provide scalability and flexibility in modern data center networks. In this case, VXLAN could be used to encapsulate Layer 2 frames within UDP packets, allowing them to be transported over the service provider’s network.

S-Tag Configuration:

Q-in-Q tagging, also known as 802.1ad, involves an outer tag (S-Tag) and an inner tag (C-Tag). The service provider network uses the S-Tag to identify and segregate customer traffic. Therefore, each campus switch must have the correct S-Tag (300 in this case) configured to ensure the service provider can correctly handle and route the traffic.

References:

Juniper Networks: Understanding VXLAN

Configuring Q-in-Q Tagging

IS-IS (Intermediate System to Intermediate System) is a link-state routing protocol used to move information efficiently within a computer network. Here is the detailed explanation about the statements:

Option A: IS-IS uses areas and an autonomous system.

This statement is correct. IS-IS organizes the network into a single autonomous system (AS), which can be divided into smaller groups called areas. Routing between areas is organized hierarchically. Each IS-IS network is treated as an autonomous system, and within that AS, multiple areas can be defined for efficient routing.

Option B: Level 1/2 routers automatically inject a default route to the nearest Level 1 router.

This statement is incorrect. Level 1/2 routers do not automatically inject default routes. Instead, they set the ATTACHED bit in their Level 1 link-state PDU when they can reach other areas, prompting Level 1 routers to use them as default gateways.

Option C: Level 2 routers must share the same area address.

This statement is incorrect. Level 2 routers operate across multiple areas and do not need to share the same area address. They are responsible for inter-area routing and thus work across different areas.

Option D: Level 1 routers route traffic between autonomous systems.

This statement is incorrect. Level 1 routers route traffic within a single area and forward inter-area traffic to Level 2 routers, which handle inter-area routing.

ConclusionGiven the above explanations, the correct statement about IS-IS is:

A. IS-IS uses areas and an autonomous system.

This is based on the hierarchical structure of IS-IS routing where the network is divided into areas within a single autonomous system.

For further details, you can refer to the Juniper IS-IS Overview.

Step 1: Identify the problem.

Devices do not support VPN NLRI, and you must prevent these devices from receiving BGP VPN routes.

Step 2: Analyze the possible solutions.

Option A: Configure an import policy on the remote peer to reject the routes when they are received.

This approach would require configuration on the remote peer, which might not always be practical or possible.

Option B: Configure an export policy on the local BGP peer to reject the VPN routes being sent to the remote peer.

This ensures the local BGP peer does not send the VPN routes to the remote peer, directly addressing the problem.

Option C: Configure a route reflector for the VPN NLRI.

This does not solve the issue of preventing the advertisement of VPN routes to non-supporting peers.

Option D: Configure the apply-vpn-export feature on the local BGP peer.

This feature ensures that the VPN export policies are applied, preventing the advertisement of VPN routes to peers that do not support VPN NLRI.

Step 3: Verify the configurations.

Option B and Option D directly address the requirement without needing configurations on the remote peer.

References:

Juniper BGP configuration guide on export policies​​​​​​.

Commands for applying export policies:

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set policy-options policy-statement term from protocol bgp-vpn

set policy-options policy-statement term then reject

set protocols bgp group export

set protocols bgp apply-vpn-export

In OSPF, the ExStart state indicates that the routers are attempting to establish a relationship and exchange information about their MTU settings. If the MTU settings do not match between the two routers on the link, it can prevent the adjacency from progressing past the ExStart state.

References:

From the image provided, you can see that the OSPF adjacency on the interface ge-0/0/2.0 is stuck in the ExStart state.

This state often suggests that there is a mismatch in the MTU settings between the routers on that interface.

To resolve this, ensure that both interfaces have the same MTU setting. You can check and set the MTU on Juniper routers using the following commands:

# Check current MTU settings

show interfaces ge-0/0/2

# Set MTU to a specific value (e.g., 1500)

set interfaces ge-0/0/2 mtu 1500

# Commit the configuration

commit