JN0-649 Sample Questions Answers

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

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​​​​.

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.

Reviewing POE Interface Information:

The exhibit shows the output of show poe interface and show poe controller commands.

The show poe interface command provides information about the PoE (Power over Ethernet) status on each interface.

Maximum Wattage Allocation:

The show poe controller output indicates that the maximum power available is 100 watts:

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Controller Maximum Power consumption Guard Management Status Lldp

index power band

0 100.00W 22.40W 10W Class AT_MODE Disabled

Thus, statement A is correct.

Power Consumption and Interface Priority:

The interface ge-0/0/11 has a high priority with a max power of 25.4W and current consumption of 11.4W:

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ge-0/0/11 Enabled ON 25.4W(L) High 11.4W 4

Given its high priority, ge-0/0/11 will continue to receive power even if the total power consumption exceeds 90 watts, as high-priority interfaces are less likely to be powered off when resources are low.

POE Status on Interfaces:

The ge-0/0/0 interface is shown as Enabled OFF, indicating PoE is not currently enabled.

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ge-0/0/0 Enabled OFF 15.4W Low 0.0W not-applicable

PoE+ Support:

The ge-0/0/10 interface has a power class of 4, which indicates support for PoE+.

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ge-0/0/10 Enabled ON 25.4W(L) Low 11.0W 4

References:

Exhibit output for show poe interface

Understanding PoE and PoE+ classes and priorities

Type 1 routes are used for per-ES auto-discovery (A-D) to advertise EVPN multi-homing mode. Remote ToR leaf devices in the EVPN network use the EVPN Type 1 route type functionality to learn the EVPN Type 2 MAC routes from other leaf devices. In this route type ESI and the Ethernet Tag ID are considered to be part of the prefix in the NLRI. Upon a link failure between ToR leaf and end server VTEP withdraws Ethernet Auto-Discovery routes (Type 1) per ES. The Juniper EVPN multi-homing Ethernet Tag value is set to the VLAN ID for ES auto-discovery/ES route types. Mass Withdrawal - Used for fast convergence during link failure scenarios between leaf devices to the end server using Type 1 EAD/ES routes.

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.

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

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​​​​.

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.

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.

 Technology Overview:

Q-in-Q (802.1ad), also known as VLAN stacking, allows multiple VLAN tags to be inserted into a single frame. This enables the carrying of multiple VLANs across a single backbone, preserving the original VLAN tags across different network segments.

 Application in Scenario:

By using Q-in-Q, the existing VLANs of the acquired company can be encapsulated within a single VLAN tag. This technique is highly efficient for carrying VLANs across a corporate backbone without altering the existing addressing scheme and with minimal configuration changes.

 Configuration Example:

Juniper Configuration:

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set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan-id 100

set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan-id-list 100-200

set interfaces ge-0/0/2 unit 0 family ethernet-switching vlan-id 300

set interfaces ge-0/0/2 unit 0 family ethernet-switching vlan-id-list 300-400

This setup ensures that VLANs 100-200 on interface ge-0/0/1 and VLANs 300-400 on interface ge-0/0/2 are bundled together, achieving the desired encapsulation.

 References:

Detailed configuration and benefits are documented in the "network-mgmt.pdf" file, which outlines the necessary steps and considerations for deploying Q-in-Q​​.

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

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.

The address range 232.0.0.0/8 is reserved for Source-Specific Multicast (SSM). This range is specifically allocated for SSM where data is sent from a specific source to the receivers.

References:

Source-Specific Multicast (SSM) Overview, RFC 4607

- Configure the local routing device so that it appears to be overloaded. You might do this when you want the routing device to participate in OSPF routing, but do not want it to be used for transit traffic. - Traffic destined to directly attached interfaces continues to reach the routing device. - When configured, the transit interface metrics are set to the maximum value of 65535. https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/ref/statement/overload-edit-protocols-ospf.html

https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/topic-map/configuring-ospf-route-control.html#id-understanding-ospf-overload-function

"Secondary interfaces are supported for LAN interfaces (the primary interface can be a LAN interface, but any secondary interfaces are treated as point-to-point unnumbered links over the LAN). In this scenario, you must ensure that there are only two routing devices on the LAN or that there are only two routing devices on the LAN that have secondary interfaces configured for a specific OSPF area." [https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/topic-map/configuring-ospf-areas.html#id-example-configuring-multiarea-adjacency-for-ospf]