Juniper JN0-480 - Data Center Specialist (JNCIS-DC)

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 catalog12. References:

Configlets Overview

Terraform Registry

The ztp.Json file on the Apstra ZTP server contains the configuration parameters for each device that is onboarded using ZTP. One of the parameters is the State, which can be one of the following values: init, ready, in_progress, done, error, or disabled. The State indicates the current status of the device in the ZTP process. For example, if the State is ready, it means that the device is ready to be onboarded by the Apstra ZTP server. If the State is done, it means that the device has completed the ZTP process and is managed by the Apstra server. The State can be manually set or changed in the ztp.Json file to control the behavior of the device during ZTP. For more information, see Apstra ZTP Configuration File. References:

Apstra ZTP Configuration File

Apstra ZTP Introduction

Configure Apstra ZTP

To implement ECMP in IP fabric using EBGP, you need to enable BGP to install multiple equal-cost paths in the routing table and to advertise them to the peers. The following actions are required to achieve this:

B. Use a load balancing policy applied to BGP as an export policy. This is true because you need to apply a load balancing policy to BGP as an export policy to allow BGP to advertise multiple paths to the same destination to the peers. By default, BGP only advertises the best path to the peers, which prevents ECMP. A load balancing policy can be configured to match the desired routes and set the multipath attribute to true. This will enable BGP to advertise up to the maximum number of paths configured by the maximum-paths command. For example, the following configuration applies a load balancing policy to BGP as an export policy for the neighbor 10.10.10.1:

policy-statement load-balance { term 1 { from { route-filter 192.168.0.0/16 exact; } then { multipath; accept; } } } protocols { bgp { group ebgp { type external; neighbor 10.10.10.1 { export load-balance; } } } }

C. Use the multipath multiple-as BGP parameter. This is true because you need to enable the multipath multiple-as BGP parameter to allow BGP to install multiple paths from different autonomous systems in the routing table. By default, BGP only installs multiple paths from the same autonomous system, which limits ECMP. The multipath multiple-as parameter can be configured under the BGP group or neighbor level. This will enable BGP to install up to the maximum number of paths configured by the maximum-paths command. For example, the following configuration enables the multipath multiple-as parameter for the BGP group ebgp:

protocols { bgp { group ebgp { type external; multipath multiple-as; } } }

The following options are incorrect because:

A. Use a load balancing policy applied to the forwarding table as an export policy is wrong because applying a load balancing policy to the forwarding table does not affect the BGP advertisement or installation of multiple paths. A load balancing policy applied to the forwarding table only affects how the traffic isdistributed among the multiple paths in the forwarding table. It does not enable ECMP in BGP.

D. Use a load balancing policy applied to BGP as an import policy is wrong because applying a load balancing policy to BGP as an import policy does not affect the BGP advertisement of multiple paths. A load balancing policy applied to BGP as an import policy only affects how the BGP routes are accepted or rejected from the peers. It does not enable ECMP in BGP. References:

IP Fabric Underlay Network Design and Implementation

Use ECMP to distribute traffic between two paths, one learned by eBGP and one learned by iBGP on a Cisco NX-OS switch

Example: Configure an EVPN-VXLAN Centrally-Routed Bridging Fabric Using EBGP

 In Juniper Apstra, a blueprint is a logical representation of the network design and configuration. When you create a new blueprint, you need to commit the changes to apply them to the network devices. However, committing the changes does not mean that the network is immediately updated and operational. It may take some time for the network to converge and reflect the new state of the blueprint. During this time, you may see some anomalies related to BGP in the main dashboard, which indicate that the BGP sessions are not established or stable between the devices. These anomalies are usually temporary and will disappear once the network converges and the BGP sessions are up and running. Therefore, the statement B is the most likely cause of these anomalies in this scenario.

The following three statements are less likely causes of these anomalies in this scenario:

You have misconfigured ASNs. This is possible, but not very likely, because Juniper Apstra provides ASN pools that can be automatically assigned to the devices based on their roles. You can also manually specify the ASNs for the devices, but you need to ensure that they are unique and consistent with the network design. If you have misconfigured ASNs, you may see some anomalies related to BGP, but they will not disappear after the network converges. You will need to fix the ASNs and commit the changes again to resolve the anomalies.

Spine-leaf links are incorrectly set. This is possible, but not very likely, because Juniper Apstra provides connectivity templates that can be used to define the spine-leaf links based on the interface maps. You can also manually specify the spine-leaf links, but you need to ensure that they are correct and match the physical cabling. If you have incorrectly set the spine-leaf links, you may see some anomalies related to BGP, but they will not disappear after the network converges. You will need to fix the spine-leaf links and commit the changes again to resolve the anomalies.

A generic system has not been configured. This is not relevant, because a generic system is a device that is not managed by Juniper Apstra, but is connected to the network. A generic system does not affect the BGP sessions between the devices that are managed by Juniper Apstra. If you have a generic system in your network, you need to configure it manually and ensure that it is compatible with the network design. A generic system does not cause any anomalies related to BGP in the main dashboard.

References:

Blueprint Summaries and Dashboard

BGP Session Flapping Probe

Probe: BGP Session Monitoring

When working with logical devices, you specify where each port group is connected by selecting the port group layout and the port speed and role (s) for each port group. The Juniper Apstra UI offers two options to the operator for the port group role: unused and generic1.

Unused: This option means that the port group is not configured or used by Apstra. This can be useful for ports that are faulty, reserved, or not part of the data center fabric1.

Generic: This option means that the port group is configured with a generic role that is not specific to any device type or function. This can be useful for ports that are used for testing, troubleshooting, or custom purposes1. References:

Logical Devices

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

According to the Juniper documentation1, 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 can be either predefined or custom. A predefined interface map is one that ships with Apstra software and supports most qualified Juniper devices. A custom interface map is one that is created by the user to meet specific requirements. An interface map can be stored in either the global catalog or the blueprint catalog. The global catalog contains all the interface maps that are available for use in any blueprint. The blueprint catalog contains the interface maps that are imported from the global catalog and used in a specific blueprint.

When a member of your organization makes changes to a predefined interface map, the following statements are correct:

Changes to interface maps in the global catalog do not affect interface maps that have already been imported into blueprint catalogs. This means that the existing blueprints that use the original version of the interface map will not be impacted by the changes. However, if you want to use the updated version of the interface map in a new or existing blueprint, you need to import it again from the global catalog.

Any changes made to predefined interface maps are discarded when Apstra is upgraded. This means that the changes will not be preserved across different versions of Apstra software. If you want to retain a customized interface map through Apstra upgrades, you need to clone the predefined interface map, give it a unique name, and customize it instead of changing the predefined one directly.

Therefore, the correct answer is A and B. Changes to interface maps in the global catalog do not affect interface maps that have already been imported into blueprint catalogs and any changes made to predefined interface maps are discarded when Apstra is upgraded. References: Edit Interface Map | Apstra 4.2 | Juniper Networks

In the Juniper Apstra UI, the Resources menu allows you to create and manage global and local resources that are used for various elements of the network design and configuration. The Resources menu includes the following three types of resources that can be assigned to the network devices and virtual networks:

ASN pools: These are pools of autonomous system numbers (ASNs) that are used for the underlay routing protocol (EBGP) between the leaf and spine devices. You can create ASN pools with either 2-byte or 4-byte ASNs, and assign them to the logical devices in the blueprint.

VNI pools: These are pools of virtual network identifiers (VNIs) that are used for the overlay network (VXLAN) between the end hosts. You can create VNI pools with a range of VNIs, and assign them to the virtual networks in the blueprint.

IP address pools: These are pools of IPv4 or IPv6 addresses that are used for various purposes in the network, such as the loopback addresses for the devices, the IP prefixes for the virtual networks, the host IP addresses for the end hosts, and the gateway IP addresses for the IRB interfaces. You can create IP address pools with a range of IP addresses, and assign them to the logical devices and virtual networks in the blueprint.

The following two types of resources are not assigned under the Resources menu:

VTEP pools: These are not resources that can be created or assigned by the user. VTEPs are VXLAN tunnel endpoints that are automatically generated by the Apstra server based on the loopback IP addresses of the devices. VTEPs are used as the source and destination IP addresses for the VXLAN tunnels in the overlay network.

Logical device pools: These are not resources that can be created or assigned by the user. Logical device pools are groups of logical devices that share the same role, interface map, and resource assignments in the blueprint. Logical device pools are used to simplify the network design and configuration by applying the same settings to multiple devices.

References:

Resources Introduction

ASN Pools (Resources)

VNI Pools (Resources)

IP Address Pools (Resources)

A Juniper Apstra rack is a physical entity that contains one or more network devices, such as leaf nodes, access switches, or generic systems. A rack is used to organize and manage the network devices in the Apstra software application. A rack has the following characteristics:

It stores information on how leaf nodes connect to generic devices. This is because a rack can include generic systems, which are devices that are not managed by Juniper Apstra, but are connected to the network. A generic system can be a server, a firewall, a load balancer, or any other device that has a networkinterface. A rack stores the information on how the leaf nodes, which are the devices that provide access to the end hosts, connect to the generic devices, such as the port number, the link speed, the LAG mode, and the roles1.

It has a rack type, which defines the type and number of leaf devices, access switches, and/or generic systems that are used in the rack. A rack type is a resource that is created in the data center design phase, and it does not specify the vendor or the model of the devices. A rack type can be predefined or custom-made, and it can be used to create multiple racks with the same structure and configuration2.

It has a rack build, which assigns the specific vendor and model of the devices to the rack. A rack build is created in the staged phase, and it uses the rack type as a template. A rack build can also assign the resources, such as the IP addresses, the ASNs, and the VNIs, to the devices in the rack3.

It has a rack deployment, which applies the network configuration and services to the devices in the rack. A rack deployment is performed in the active phase, and it uses the rack build as a reference. A rack deployment can also monitor the network performance and compliance of the devices in the rack4.

The following three statements are incorrect in this scenario:

It stores information on how pods connect to super spines. This is not true, because a rack does not store any information on the pod or the super spine level of the network. A pod is a cluster of leaf and spine devices that form a 3-stage Clos topology, and a super spine is a device that connects multiple pods in a 5-stage Clos topology. A rack only stores information on the leaf and the access level of the network1.

It stores IP address and ASN pool information. This is not true, because a rack does not store any information on the IP address and ASN pools. IP address and ASN pools are resources that are created in the data center design phase, and they contain a range of IP addresses and ASNs that can be assigned to the devices and the virtual networks. A rack only uses the IP address and ASN pools to assign the resources to the devices in the rack build2.

It stores device port data rates and vendor information. This is not true, because a rack does not store any information on the device port data rates and vendor information. The device port data rates and vendor information are specified in the rack build, which assigns the specific vendor and model of the devices to the rack. A rack only uses the rack build to apply the network configuration and services to the devices in the rack deployment3.

References:

Racks (Staged)

Rack Types (Datacenter Design)

Rack Builds (Staged)

Racks (Active)