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

Understanding the Problem:

The ports between the access switches and the distribution switch are shutting down when the L2PT configuration is applied. This typically happens due to a mismatch in port configurations or protocol incompatibilities.

Examining the Configurations:

L2PT (Layer 2 Protocol Tunneling) allows tunneling of Layer 2 traffic, which includes protocols like STP (Spanning Tree Protocol), CDP (Cisco Discovery Protocol), VTP (VLAN Trunking Protocol), etc. over a Layer 2 network.

If the L2PT is applied on access ports, it may lead to conflicts or shut down the ports as access ports are typically not configured to handle Layer 2 protocol traffic beyond their designated VLAN.

Solution: Configure Trunk Ports:

By configuring the links between the access switches and the distribution switch as trunk ports, you allow multiple VLANs to be carried over a single physical link. Trunk ports can carry tagged traffic for multiple VLANs, which includes the tunneled Layer 2 protocols.

This setup prevents the ports from shutting down and enables the correct tunneling of Layer 2 protocols.

References:

Juniper Documentation on L2PT Configuration

Troubleshooting Layer 2 Protocol Tunneling Issues

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

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

The leaf node is not configured for the family evpn NLRI (D):

The exhibit shows that there is an unsupported capability NP error for AFI 1, SAFI 70. This indicates that the leaf node is not configured to support the EVPN (Ethernet VPN) address family.

References:

The BGP configuration and troubleshooting details can be found in "Juniper Commands.pdf" and related EVPN configuration documents​​​​.

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 EVPN Route Types:

EVPN (Ethernet VPN) is used for providing Ethernet multipoint services over MPLS or VXLAN networks.

EVPN Route Types:

Type 1 (Ethernet Auto-Discovery Route): Used for auto-discovery of PEs and for detecting multi-homed devices.

Type 2 (MAC/IP Advertisement Route):

Carries endpoint MAC address information.

Carries endpoint IP address information.

Facilitates MAC learning and IP-to-MAC binding distribution.

Type 3 (Inclusive Multicast Route):

Carries replication information.

Used for forwarding multicast and broadcast traffic.

Type 5 (IP Prefix Route): Carries IP prefixes for inter-subnet connectivity, but not replication information.

Verification:

Type 2 routes are crucial for distributing MAC and IP information about endpoints.

Type 3 routes are used to manage multicast traffic effectively.

References:

Juniper EVPN Configuration Guide

Understanding EVPN Route Types

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

Single supplicant mode authenticates only the first end device that connects to an authenticator port. All other end devices connecting to the authenticator port after the first has connected successfully, whether they are 802.1X-enabled or not, are permitted access to the port without further authentication. If the first authenticated end device logs out, all other end devices are locked out until an end device authenticates. Single-secure supplicant mode authenticates only one end device to connect to an authenticator port. No other end device can connect to the authenticator port until the first logs out

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

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​​.

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 troubleshooting an EVPN-VXLAN IP fabric loop, the following steps are crucial:

Issue the show route table bgp.evpn.0 command on Leaf2 and verify that Type 4 routes are present: Type 4 routes indicate EVPN Ethernet Segment routes, which are essential for detecting and mitigating loops.

Issue the show route table bgp.evpn.0 command on Leaf2 and verify that Type 3 routes are present: Type 3 routes (Inclusive Multicast Ethernet Tag routes) ensure that multicast and broadcast traffic is properly handled, helping identify and troubleshoot loop issues.

References:

The commands for verifying BGP EVPN routes are standard in troubleshooting EVPN-VXLAN fabrics.

Documentation from "Useful Juniper Commands.txt" and "Juniper Commands.pdf" which provide command references for verifying EVPN route types​​​​.

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​​​​.

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

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 Multicast Listener Registration Protocols:

Multicast listener registration protocols are used to manage multicast group memberships on a network.

They allow devices to join or leave multicast groups dynamically.

Protocols Supported by Junos:

MLD (Multicast Listener Discovery):

Used for IPv6 multicast group management. It is the IPv6 equivalent of IGMP.

MLD allows routers to discover multicast listeners on a network.

IGMP (Internet Group Management Protocol):

Used for IPv4 multicast group management.

IGMP enables hosts to join and leave multicast groups and allows routers to manage multicast group memberships.

Verification and Configuration in Junos:

MLD and IGMP are supported on Juniper devices running the Junos operating system.

Configuration examples:

IGMP:

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set protocols igmp interface ge-0/0/1.0

MLD:

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set protocols mld interface ge-0/0/1.0

References:

Juniper IGMP Configuration Guide

Juniper MLD Configuration Guide

Step 1: Identify the requirement.

You need an OSPF area that only contains intra-area route information in the form of Type 1 and Type 2 LSAs.

Step 2: Analyze the possible OSPF area types.

Option A: Totally non-to-stubby area.

Option B: Totally stubby area.

Option C: Stub area.

Option D: Non-to-stubby area.

Step 3: Understand OSPF area types.

Totally Stubby Area (Option B): Only allows Type 1 and Type 2 LSAs and blocks Type 3, 4, and 5 LSAs. It uses a default route to represent external routes.

This fits the requirement of containing only intra-area routes.

References:

Juniper OSPF configuration guide on area types​​​​.

Commands for configuring a totally stubby area:

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set protocols ospf area stub no-summaries