Juniper JN0-480 Exam Questions

In the case of IP Clos data center five-stage fabric design, the super spines are the devices that provide the highest level of aggregation in the network. They have two main roles:

Super spines are used to interconnect two different data center pods. A pod is a cluster of leaf and spine devices that form a 3-stage Clos topology. A 5-stage Clos topology consists of multiple pods that are connected by the super spines. This allows for scaling the network to support more devices and bandwidth.

Super spines connect to all spine devices within the five-stage architecture. The spine devices are the devices that provide the second level of aggregation in the network. They connect to the leaf devices, which are the devices that provide access to the end hosts. The super spines connect to all the spine devices in the network, regardless of which pod they belong to. This provides any-to-any connectivity between the pods and enables optimal routing and load balancing.

The following two statements are incorrect in this scenario:

Super spines are used to connect leaf nodes within a data center pod. This is not true, because the leaf nodes are connected to the spine nodes within the same pod. The super spines do not connect to the leaf nodes directly, but only through the spine nodes.

Super spines are always connected to an external data center gateway. This is not true, because the super spines are not necessarily involved in the external connectivity of the data center. The external data center gateway is a device that provides the connection to the outside network, such as the Internet or another data center. The external data center gateway can be connected to the super spines, the spine nodes, or the leaf nodes, depending on the design and the requirements of the network.

5-stage Clos Architecture --- Apstra 3.3.0 documentation

5-Stage Clos Architecture | Juniper Networks

Extreme Fabric Automation Administration Guide

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 network interface.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.

Racks (Staged)

Rack Types (Datacenter Design)

Rack Builds (Staged)

Racks (Active)

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 standard1. 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 VNI2.

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 network1.

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 standard1. Alphanumeric values are values that contain both letters and numbers, such as ABC123 or 1A2B3C.

Virtual Extensible LAN (VXLAN) Overview

EVPN LAGs in EVPN-VXLAN Reference Architectures

To answer this question, we need to understand the concept of ESI values in EVPN LAGs. An ESI is a 10-byte value that identifies an Ethernet segment, which is a set of links that connect a multihomed device (such as a server) to one or more PE devices (such as leaf switches) in an EVPN network. The same ESI value must be configured on all the PE devices that connect to the same Ethernet segment. This allows the PE devices to form an EVPN LAG, which supports active-active or active-standby multihoming for the device. The ESI value can be manually configured (type 0) or automatically derived from LACP (type 1) or other methods. In the exhibit, Server A is connected to two leaf switches (QFX 5210) using a LAG with LACP enabled. Server B is connected to three leaf switches (QFX 5120) using a LAG with LACP enabled. Based on this information, the following statements are correct about ESI values for the server connections to the fabric:

C) A valid ESI value for Server A is 0x00.10.10.10.10.10.10.10.10.10. This is true because this ESI value can be automatically derived from the LACP configuration on the QFX 5210 devices. The LACP system ID is usually based on the MAC address of the device, and the LACP administrative key is a 2-byte value that identifies the LAG. For example, if the MAC address of the QFX 5210 device is 00:10:10:10:10:10 and the LAG ID is 10, then the LACP system ID is 00:10:10:10:10:10 and the LACP administrative key is 00:0A. The ESI value is then derived by concatenating the LACP system ID and the LACP administrative key, resulting in 00:10:10:10:10:10:00:0A. This ESI value can be represented in hexadecimal notation as 0x00.10.10.10.10.10.00.0A, or padded with zeros as 0x00.10.10.10.10.10.00.0A.00.00. This ESI value must be configured on both QFX 5210 devices that connect to Server A.

D) A valid ESI value for Server B is 0x00.00.00.00.00.00.00.00.00.00. This is true because this ESI value is a reserved value that indicates a single-homed device. Server B is connected to three leaf switches (QFX 5120) using a LAG, but it is not multihomed to any of them. This means that Server B does not need an ESI value to form an EVPN LAG with any of the leaf switches. Instead, Server B can use the reserved ESI value of 0x00.00.00.00.00.00.00.00.00.00, which indicates that it is a single-homed device and does not participate in any EVPN LAG. This ESI value must be configured on all three QFX 5120 devices that connect to Server B. The following statements are incorrect about ESI values for the server connections to the fabric:

A) A valid ESI value for Server A is 0x00.00.00.00.00.00.00.00.00.00. This is false because this ESI value is a reserved value that indicates a single-homed device. Server A is connected to two leaf switches (QFX 5210) using a LAG with LACP enabled, which means that it is multihomed to both of them. This means that Server A needs an ESI value to form an EVPN LAG with the leaf switches. The ESI value must be unique and non-zero for each Ethernet segment, so the reserved ESI value of 0x00.00.00.00.00.00.00.00.00.00 is not valid for Server A.

B) A valid ESI value for Server B is 0x00.20.20.20.20.20.20.20.20.20. This is false because this ESI value is not derived from the LACP configuration on the QFX 5120 devices. Server B is connected to three leaf switches (QFX 5120) using a LAG with LACP enabled, but it is not multihomed to any of them. This means that Server B does not need an ESI value to form an EVPN LAG with any of the leaf switches. Instead, Server B can use the reserved ESI value of 0x00.00.00.00.00.00.00.00.00.00, which indicates that it is a single-homed device and does not participate in any EVPN LAG. The ESI value of 0x00.20.20.20.20.20.20.20.20.20 is not valid for Server B, and it may cause conflicts with other Ethernet segments that use the same ESI value.Reference:

Ethernet Segment Identifiers, ESI Types, and LACP in EVPN LAGs

Understanding Automatically Generated ESIs in EVPN Networks

Ethernet Segment in EVPN: All You Need to Know

According to the Juniper documentation1, 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.Reference:Commit / Revert Changes to Blueprint | Apstra 4.2 | Juniper Networks