Juniper JN0-649 Enterprise Routing and Switching Professional (JNCIP-ENT) Exam Practice Test

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.

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

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

To ensure that each host is placed on a separate VLAN when using an unmanaged switch between the hosts and the EX Series switch:

Configure an input firewall filter on interface ge-0/0/3 to match the source MAC or IP address of the hosts to assign the VLANs:

By configuring an input firewall filter, you can match the source MAC or IP address of incoming traffic and assign the appropriate VLAN based on these criteria.

This method ensures that even though the switch between hosts and EX Series is unmanaged, VLAN assignments are still properly enforced at the EX Series switch.

Configuration Example:

set firewall family ethernet-switching filter VLAN-assignment term VLAN100 from source-mac-address xx:xx:xx:xx:xx:xx

set firewall family ethernet-switching filter VLAN-assignment term VLAN100 then vlan-assignment vlan 100

set firewall family ethernet-switching filter VLAN-assignment term VLAN200 from source-mac-address yy:yy:yy:yy:yy:yy

set firewall family ethernet-switching filter VLAN-assignment term VLAN200 then vlan-assignment vlan 200

set firewall family ethernet-switching filter VLAN-assignment term VLAN300 from source-mac-address zz:zz:zz:zz:zz:zz

set firewall family ethernet-switching filter VLAN-assignment term VLAN300 then vlan-assignment vlan 300

set interfaces ge-0/0/3 unit 0 family ethernet-switching filter input VLAN-assignment

References:

The command references from "Useful Juniper Commands.txt" and network configuration guides provide details on firewall filters and VLAN assignments​​.

https://www.juniper.net/documentation/us/en/software/junos/routing-policy/bgp/topics/example/bgp-advertise-peer-as.html

Understanding BGP Communities:

BGP communities are used to tag routes with certain attributes to control their distribution and processing.

The no-export community ensures that the routes tagged with this community are not advertised to any BGP peers outside the local AS (Autonomous System).

Applying the no-export Community:

To ensure that all routes in the 10.0.0.0/8 address range are not advertised outside the AS, the no-export community should be assigned to these routes. This prevents the routes from being propagated beyond the local AS boundary.

References:

Juniper BGP Communities

Configuring BGP Community Attributes

Reviewing MST Configuration:

The configuration shown in the exhibit indicates MST (Multiple Spanning Tree) configuration for DS-1 and DS-2 switches.

For DS-1:

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mstp {

configuration-name Region-1;

revision-level 1;

interface ge-0/0/8;

interface ge-0/0/9;

interface ge-0/0/10;

interface ge-0/0/12;

msti 1 {

bridge-priority 4k;

vlan 10-19;

}

msti 2 {

bridge-priority 8k;

vlan 20-29;

}

}

For DS-2:

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mstp {

configuration-name Region-1;

revision-level 1;

interface ge-0/0/8;

interface ge-0/0/9;

interface ge-0/0/10;

interface ge-0/0/12;

msti 1 {

bridge-priority 8k;

vlan 10-19;

}

}

Understanding Bridge Priority:

In MSTP, the switch with the lowest bridge priority becomes the root bridge for the respective MST instance.

For MSTI 1:

DS-1 bridge-priority is 4k (4096)

DS-2 bridge-priority is 8k (8192)

Thus, DS-1 will be the root bridge for MSTI 1.

For MSTI 2:

DS-1 bridge-priority is 8k (8192)

DS-2 does not participate in MSTI 2.

Thus, DS-1 will be the root bridge for MSTI 2.

Analyzing VLAN Assignments:

DS-1 MSTI 1: VLANs 10-19, priority 4k

DS-1 MSTI 2: VLANs 20-29, priority 8k

DS-2 MSTI 1: VLANs 10-19, priority 8k

DS-2 does not have MSTI 2 configuration.

Conclusion:

DS-1 is the root bridge for MSTI 1 (C)

DS-2 does not participate in MSTI 2 (eliminates A)

DS-1 is the root bridge for MSTI 2 (D)

DS-2 is not the root bridge for MSTI 1 (eliminates B)

References:

Configuration snippets

Understanding of MSTP priorities and root bridge election

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

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

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.

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

Dynamic VLAN assignment using 802.1X authentication relies on vendor-specific attributes (VSAs) to assign VLANs dynamically based on the authentication results. The modes that support using VSAs for dynamic VLAN assignment are:

Single-Secure Supplicant Mode: This mode supports a single secure client on a port and can use VSAs to dynamically assign VLANs based on the authentication result.

Multiple Supplicant Mode: This mode supports multiple clients on a single port, each with its own authentication session, and can use VSAs to dynamically assign VLANs.

References:

The Juniper documentation and configuration guides discuss the capabilities of these modes in supporting dynamic VLAN assignment through VSAs. Specific configuration examples and guidelines can be found in the documents:

Useful Juniper Commands.txt

Tech Ops Managed Router Juniper Install Guide

# Example of enabling single-secure supplicant mode

set protocols dot1x authenticator interface ge-0/0/1.0 supplicant multiple

# Example of enabling multiple supplicant mode

set protocols dot1x authenticator interface ge-0/0/1.0 supplicant multiple

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.

To ensure proper functioning within an MST (Multiple Spanning Tree) region, the following parameters must match across all switches:

Revision number:

The revision number identifies the version of the MST configuration. All switches within the same MST region must have the same revision number to ensure consistency.

MSTI-to-VLAN mapping:

The MSTI (Multiple Spanning Tree Instance) to VLAN mapping must be identical on all switches. This mapping ensures that each VLAN is assigned to the correct spanning tree instance.

Configuration name:

The configuration name (or region name) must be the same across all switches. This name uniquely identifies the MST region and must be consistent to ensure switches recognize they are part of the same region.

References:

The MSTP configuration requirements are detailed in Juniper network configuration guides and standards documents on MSTP​​​​.

Junos OS supports both underlay and ingress replication for BUM (Broadcast, Unknown unicast, and Multicast) traffic forwarding in EVPN-VXLAN deployments. Ingress replication is used for efficient multicast traffic distribution in networks where underlay multicast is not available.

References:

EVPN-VXLAN Configuration Guide, Juniper Networks

Juniper Networks Documentation on EVPN-VXLAN

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​​​​.