JN0-649 Enterprise Routing and Switching Professional (JNCIP-ENT) Questions and Answers

To understand what routes the BGP neighbor can and cannot advertise, we need to analyze the output provided in the exhibit. Here are the key points from the BGP neighbor configuration:

Address Families Configured:

The neighbor has the EVPN (Ethernet VPN) address family configured.

There is no indication of L3 VPN (Layer 3 Virtual Private Network) address family configuration in the provided output.

Advertised NLRI (Network Layer Reachability Information):

The output shows that the BGP neighbor advertises EVPN NLRI and does not have configurations to advertise L3 VPN NLRI.

Session Details:

The BGP session is established and in sync with the EVPN address family.

Based on these observations, the correct statements about the BGP neighbor's capabilities are:

C. The BGP neighbor can advertise EVPN related routes.

The exhibit confirms that the EVPN address family is configured and EVPN NLRI is advertised.

D. The BGP neighbor cannot advertise L3 VPN related routes.

There is no configuration or NLRI for L3 VPN in the exhibit, indicating that L3 VPN routes cannot be advertised by this neighbor.

References:

Useful Juniper Commands.txt

Tech Ops Managed Router Juniper Install Guide

In summary, the BGP neighbor in the exhibit can advertise EVPN routes but cannot advertise L3 VPN routes based on the provided configuration and session details.

B - because only one next hop in forwarding table C- becuse TTL=1 limiting bgp connection to be established only over loopbacks interface https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/topic-map/multihop-sessions.html Use the multihop statement to alter the default use of the neighbor 's physical address. In addition, you can also specify a time-to-live (TTL) value in the BGP packets to control how far they propagate. We use a TTL value of 1 to ensure that the session cannot be established across any other backdoor links in the network.

Understanding the Configuration:

The provided configuration and output snippets show how traffic is classified and assigned to different forwarding classes based on the IP precedence values.

The inet-precedence classifier maps specific IP precedence values to forwarding classes with associated loss priorities.

Review of Classifiers:

IP Precedence Value 100:

The IP precedence value 100 in binary is represented as 100 (binary for 4).

Matching with Classifiers:

According to the configuration shown in the exhibit:

classifiers {

inet-precedence cos;

}

The classifier cos maps the following:

forwarding-class expedited-forwarding;

loss-priority low code-points 100;

Conclusion:

The IP precedence value 100 matches the expedited-forwarding forwarding class with low loss-priority as per the configuration.

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

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

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

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

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.

shell

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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.

shell

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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​​​​.

To implement fault-tolerant RPs (Rendezvous Points) in a multicast network, the following two solutions are appropriate:

Use MSDP with statically defined RPs:

MSDP (Multicast Source Discovery Protocol) is used to share multicast source information between multiple RPs in different domains or within the same domain. It allows for RP redundancy by ensuring that if one RP fails, another RP can take over the role and continue to manage multicast group memberships.

LLDP-MED (Link Layer Discovery Protocol-Media Endpoint Discovery) is an extension of LLDP (Link Layer Discovery Protocol) that provides additional functionalities specifically for voice over IP (VoIP) devices, including automatic negotiation of power requirements. This protocol is essential for automatically negotiating power with IP phones when they are connected to EX Series switches.

Steps:

Enable LLDP-MED:

set protocols lldp-med

Configure LLDP-MED on the interfaces:

set interfaces ge-0/0/0 unit 0 family ethernet-switching port-mode access

set interfaces ge-0/0/0 unit 0 family ethernet-switching interface-mode access

set interfaces ge-0/0/0 unit 0 family ethernet-switching vlan members default

set interfaces ge-0/0/0 unit 0 family ethernet-switching storm-control default

Commit the configuration:

References:

Useful Juniper Commands.txt

Tech Ops Managed Router Juniper Install Guide

802.1X Authentication and Re-authentication:

802.1X is used for network access control, where clients (supplicants) authenticate through a RADIUS server.

If a client cannot re-authenticate, the network access behavior depends on the configured action.

Permit Access Configuration:

The permit action ensures that the client continues to have network access if re-authentication fails.

This is crucial in scenarios where continuous access is needed despite temporary authentication issues.

Configuration Syntax:

On the Juniper device, configure the permit action:

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set protocols dot1x authenticator authentication-profile re-authentication permit

References:

Juniper documentation on 802.1X configuration

Understanding 802.1X re-authentication and access control mechanisms