JN0-480 Data Center Specialist (JNCIS-DC) Questions and Answers

VXLAN VNIs are virtual network identifiers that are used to identify and isolate Layer 2 segments in the overlay network. VXLAN VNIs have the following characteristics:

VNIs can have over 16 million unique values.  This is because VXLAN VNIs are 24-bit fields that can range from 4096 to 16777214, according to the VXLAN standard 1 . This allows VXLAN to support a large number of Layer 2 segments and tenants in the network.

VNIs identify a broadcast domain. This is because VXLAN VNIs are used to group the end hosts that belong to the same Layer 2 segment and can communicate with each other using VXLAN tunnels. The VXLAN tunnels are established using the VTEP information that is distributed by EVPN. The VTEPs are VXLAN tunnel endpoints that perform the VXLAN encapsulation and decapsulation.  The VXLAN tunnels preserve the Layer 2 semantics and support the broadcast, unknown unicast, and multicast traffic within the same VNI 2 .

The following two statements are incorrect in this scenario:

VNIs identify a collision domain. This is not true, because VXLAN VNIs do not identify a collision domain, which is a network segment where data packets can collide with each other. VXLAN VNIs identify a broadcast domain, which is a network segment where broadcast traffic can reach all the devices.  Collision domains are not relevant in VXLAN networks, because VXLAN uses MAC-in-UDP encapsulation and IP routing to transport the Layer 2 frames over the Layer 3 network 1 .

VNIs are alphanumeric values. This is not true, because VXLAN VNIs are numeric values, not alphanumeric values.  VXLAN VNIs are 24-bit fields that can range from 4096 to 16777214, according to the VXLAN standard 1 . Alphanumeric values are values that contain both letters and numbers, such as ABC123 or 1A2B3C.

References :

Virtual Extensible LAN (VXLAN) Overview

EVPN LAGs in EVPN-VXLAN Reference Architectures

According to the Juniper documentation 1 , an interface map is a configuration template that maps interfaces between logical devices and physical hardware devices (represented with device profiles) while adhering to vendor specifications. An interface map specifies a connection between the interfaces of two devices, such as a leaf and a spine, a leaf and a server, or a leaf and an external gateway. An interface map can also specify port transformations, such as breaking out a 40 GbE port into four 10 GbE ports, or disabling unused ports. An interface map can be used to achieve the intended network configuration rendering and to enable features such as LAG, ESI-LAG, or MLAG. Therefore, the correct answer is B. An interface map specifies a connection between the interfaces of two devices.  References :  Interface Maps (Datacenter Design)

 According to the Juniper documentation 1 , the Revert button is located on the Uncommitted tab of the blueprint page. The Uncommitted tab shows the changes that have been staged but not yet committed to the network. The Revert button allows you to discard any uncommitted changes and revert to the last committed state of the blueprint. This is useful if you want to cancel the changes that you have made or if you want to start over with a fresh slate. Therefore, the correct answer is B. The Revert button deletes any uncommitted changes within Apstra.  References :  Commit / Revert Changes to Blueprint | Apstra 4.2 | Juniper Networks

According to the Juniper documentation 1 , a routing zone is an L3 domain, the unit of tenancy in multi-tenant networks. You create routing zones for tenants to isolate their IP traffic from one another, thus enabling tenants to re-use IP subnets. In addition to being in its own VRF, each routing zone can be assigned its own DHCP relay server and external system connections. You can create one or more virtual networks within a routing zone, which means a tenant can stretch its L2 applications across multiple racks within its routing zone. For virtual networks with Layer 3 SVI, the SVI is associated with a Virtual Routing and Forwarding (VRF) instance for each routing zone isolating the virtual network SVI from other virtual network SVIs in other routing zones. If you’re using multiple routing zones, external system connections must be from leaf switches in the fabric. Routing between routing zones must be accomplished with external systems. Therefore, the correct answer is D. Use interconnection through an external gateway.  References :  Routing Zones

Juniper Apstra supports three deploy modes for devices:  Deploy ,  Drain , and  Ready .  These modes determine the configuration and state of the devices in the data center fabric 1 2 .

Deploy : This mode applies the full Apstra-rendered configuration to the device, according to the Apstra Reference Design.  The device state becomes  IS-ACTIVE  and the device is ready to carry traffic in the fabric 1 2 .

Drain : This mode adds a “drain” configuration to the device, which prevents any new traffic from entering the device.  The device state becomes  IS-READY  and the device is prepared for maintenance or decommissioning 1 2 .

Ready : This mode removes the Apstra-rendered configuration from the device, leaving only the basic configuration such as device hostname, interface descriptions, and port speed/breakout.  The device state becomes  IS-READY  and the device is not part of the fabric 1 2 .  References :

Device Configuration Lifecycle

Set Deploy Mode (Datacenter)

Device A serves as a spine in an IP fabric. An IP fabric is a network architecture that uses a spine-leaf topology to provide high performance, scalability, and reliability for data center networks. A spine-leaf topology consists of two layers of devices: spine devices and leaf devices. Spine devices are the core devices that interconnect all the leaf devices using equal-cost multipath (ECMP) routing. Leaf devices are the edge devices that connect to the servers, storage, or other network devices. In the exhibit, Device A is connected to four leaf devices using multiple links, which indicates that it is a spine device. The other options are incorrect because:

A. leaf is wrong because a leaf device is an edge device that connects to the servers, storage, or other network devices. In the exhibit, Device A is not connected to any servers, storage, or other network devices, but only to four leaf devices, which indicates that it is not a leaf device.

C. super spine is wrong because a super spine device is a higher-level device that interconnects multiple spine devices in a large-scale IP fabric. A super spine device is typically used when the number of leaf devices exceeds the port density of a single spine device. In the exhibit, Device A is not connected to any other spine devices, but only to four leaf devices, which indicates that it is not a super spine device.

D. server is wrong because a server device is a compute or storage device that connects to a leaf device in an IP fabric. A server device is typically the end host that provides or consumes data in the network. In the exhibit, Device A is not connected to any leaf devices, but only to four leaf devices, which indicates that it is not a server device.  References :

IP Fabric Underlay Network Design and Implementation

IP Fabric Overview

IP Fabric Architecture

According to the Juniper documentation 1 , an ESI-LAG is a link aggregation group (LAG) that spans two or more devices and is identified by an Ethernet segment identifier (ESI). An ESI-LAG provides redundancy and load balancing for a multihomed server in an EVPN-VXLAN network. To configure an ESI-LAG, you need to ensure that the following requirements are met:

The LACP system ID on both devices must be the same. This ensures that the LACP protocol can negotiate the LAG parameters and form a single logical interface for the server.

The ESI ID on both devices must be the same. This ensures that the EVPN control plane can advertise the ESI-LAG as a single Ethernet segment and synchronize the MAC and IP addresses of the server across the devices.

The VLAN ID and VNI on both devices must be the same. This ensures that the server can communicate with other hosts in the same virtual network and that the VXLAN encapsulation and decapsulation can work properly.

In the exhibit, the LACP system ID and the ESI ID on both devices are different, which prevents the ESI-LAG from coming up as multihomed. Therefore, the correct answer is B and D. The LACP system ID on both devices must be the same and the ESI ID on both devices must be the same.  References :  ESI-LAG Made Easier with EZ-LAG ,  Example: Configuring an ESI on a Logical Interface With EVPN-MPLS Multihoming ,  Introduction to EVPN LAG Multihoming

In the Juniper Apstra UI, you can create VNI pools for virtual networks that use VXLAN encapsulation in the overlay network. A VNI pool is a resource pool that contains a range of VNIs that can be assigned to the virtual networks.  The valid VNI range for a VNI pool is 4096 through 16777214, according to the VXLAN standard 1 . Therefore, the statement B is correct in this scenario.

The following three statements are incorrect in this scenario:

Any range is acceptable for the VNI pool.  This is not true, because the VNI range has a lower and upper limit defined by the VXLAN standard 1 . The lower limit is 4096, and the upper limit is 16777214. Any VNI outside this range is invalid and cannot be used for VXLAN encapsulation.

The valid VNI range is 2 through 4096. This is not true, because the VNI range does not start from 2, but from 4096.  The VNIs from 2 to 4095 are reserved and cannot be used for VXLAN encapsulation 1 .

The valid VNI range is 1 through 10000.  This is not true, because the VNI range does not include 1, which is also reserved and cannot be used for VXLAN encapsulation 1 .  The VNI range also does not end at 10000, but at 16777214, which is the maximum possible value for a 24-bit VNI field 1 .

References :

VNI Pools (Resources)

Referring to the exhibit, the image shows a user interface of the Juniper Apstra software application, which is used for network management and configuration. The image shows the Virtual Networks table under the Resources menu, which displays the details of the VLANs and VXLANs in the network. The table has 11 columns, but only 9 are visible in the image. The other two columns are IPv6 Connectivity and IPv6 Subnet, which are hidden by default. To display the IPv6 subnets for all of the listed VXLANs, the user needs to select Columns, then select IPv6 Subnet. This will show the IPv6 Subnet column in the table, which will display the IPv6 addresses assigned to the VXLANs from the IPv6 pools. For more information, see  Virtual Networks (Resources) .  References :

Virtual Networks (Resources)

IPv6 Pools (Resources)

Apstra User Guide

Referring to the exhibit, the image shows the Racks table under the Staged menu in the Juniper Apstra UI. The Racks table displays the details of the racks that are used in the blueprint, such as the name, rack type, and date.  The rack type is a resource that defines the type and number of leaf devices, access switches, and/or generic systems that are used in rack builds 1 . The image shows seven racks in the table, but only two rack types: BorderLeaf and ServerRack. Therefore, the statement D is correct in this scenario.

The following three statements are incorrect in this scenario:

A. six. This is not true, because there are not six rack types in the table, but only two. The number six corresponds to the number of racks that have the same rack type: ServerRack.

B. three. This is not true, because there are not three rack types in the table, but only two. The number three does not correspond to any relevant information in the table or the image.

C. seven. This is not true, because there are not seven rack types in the table, but only two. The number seven corresponds to the total number of racks in the table, not the rack types.

References :

Rack Types (Datacenter Design)

Racks (Staged)

To configure a static route for traffic to exit a configured routing zone, you need to use the Connectivity Templates feature in the Juniper Apstra UI. A Connectivity Template is a set of configuration parameters that can be applied to a device or a group of devices in a blueprint. You can use Connectivity Templates to configure static routes, BGP, OSPF, and other network services. To create a Connectivity Template, you need to go to the Staged tab and select Connectivity Templates from the left menu. Then, you can click on the + icon to create a new template. You can specify the name, description, and scope of the template. The scope determines which devices or device groups the template will be applied to. You can also specify the order of the template, which determines the priority of the template when multiple templates are applied to the same device. After creating the template, you can add configuration items to the template. To add a static route, you need to select Static Route from the drop-down menu and enter the destination network, subnet mask, and next-hop IP address. You can also specify the administrative distance and the track object for the static route. After adding the configuration items, you need to save the template and commit the changes to the blueprint. The other options are incorrect because:

A. under Active - > Virtual - > Routing Zones is wrong because this option allows you to view and modify the existing routing zones, but not to configure static routes for them.

B. under Staged - > Virtual - > Routing Zones is wrong because this option allows you to create and delete routing zones, but not to configure static routes for them.

C. under Active - > Connectivity Templates is wrong because this option allows you to view the existing connectivity templates, but not to create or modify them.  References :

Connectivity Templates

Data Center Automation Using Juniper Apstra

To apply a configlet to a specific device using Juniper Apstra, you need to specify the device’s hostname and tags. The hostname is the unique identifier of the device in the Apstra system, and the tags are the labels that you can assign to the device to group it with other devices that share the same characteristics.  You can use the hostname and tags to filter the devices that you want to apply the configlet to in the blueprint catalog 1 2 .  References :

Configlets Overview

Terraform Registry

When an agent installation is successful, devices are placed into the Out of Service Quarantined (OOS-QUARANTINED) state using the Juniper Apstra UI. This state means that the device is not yet managed by Apstra and has not been assigned to any blueprint. The device configuration at this point is called Pristine Config.  To make the device ready for use in a blueprint, you need to acknowledge the device, which changes its state to Out of Service Ready (OOS-READY) 1 2 .  References :

Managing Devices

AOS Device Configuration Lifecycle

According to the Juniper documentation 1 , a configlet is a configuration template that augments Apstra’s reference design with non-native device configuration. They consist of one or more generators. Each generator specifies a NOS type (config style), when to render the configuration, and CLI commands (and file name as applicable). Some applications for configlets include the following:

Syslog

SNMP access policy

TACACS / RADIUS

Management ACLs

Control plane policing

NTP

Username / password

Therefore, the correct answer is C and D. syslog configuration and NTP configuration. These are examples of non-native device configuration that can be added using a configlet. Static route configuration and policy configuration are not applicable in this scenario, because they are part of the reference design configuration that should not be replaced or modified by a configlet.  References :  Configlets (Datacenter Design) ,  Configlet Examples (Design)

When an agent installation is successful, devices are placed into the Out of Service Quarantined (OOS-QUARANTINED) state using the Juniper Apstra UI. This state means that the device is not yet managed by Apstra and has not been assigned to any blueprint. The device configuration at this point is called Pristine Config. To make the device ready for use in a blueprint, you need to acknowledge the device, which is a manual action that confirms the device identity and ownership.  Acknowledging the device changes its status to Out of Service Ready (OOS-READY) 1 2 .  References :

Managing Devices

AOS Device Configuration Lifecycle

The leaf device in AS 65000 will receive three routes for the 10.100.0.0/16 prefix, one from each spine device in AS 65001, AS 65002, and AS 65003. Since ECMP load balancing is enabled, the leaf device will install all three routes in its routing table and distribute the traffic among them. The other options are incorrect because:

B. 1 is wrong because the leaf device will not receive only one route for the prefix. It will receive multiple routes from different spine devices and use ECMP to load balance among them.

C. 2 is wrong because the leaf device will not receive only two routes for the prefix. It will receive three routes from three spine devices, as explained above.

D. 4 is wrong because the leaf device will not receive four routes for the prefix. It will receive three routes from three spine devices, as explained above. The fourth spine device in AS 65004 is not directly connected to the leaf device and will not advertise the prefix to it.  References :

IP Fabric Underlay Network Design and Implementation

BGP Multipath load sharing iBGP and eBGP

ECMP Load Balancing