JN0-649 Questions and 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

 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​​.

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

Understanding EVPN Route Types:

EVPN routes facilitate Layer 2 and Layer 3 connectivity across data centers.

Layer 2 and Layer 3 Connectivity:

For Layer 3 connectivity across data centers, where Layer 2 does not extend, IP prefixes need to be communicated.

Type 5 Routes:

Type 5 (IP Prefix Route):

Used to distribute IP prefixes between data centers.

Ensures that Layer 3 connectivity is established without extending Layer 2 domains.

References:

Juniper EVPN Type 5 Routes

Configuring EVPN for Data Center Interconnect

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.

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

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

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

Anycast RP uses Multicast Source Discovery Protocol (MSDP) to discover and maintain a consistent view of the active sources. nclude the anycast-pim statement to configure anycast RP without MSDP (for example, if IPv6 is used for multicasting). The other RP routers that share the same IP address are configured using the rp-set statement. https://www.juniper.net/documentation/us/en/software/junos/multicast/topics/topic-map/mcast-pim-anycast-rp.html

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