Ace Your JN0-480 Juniper Certification Exam

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. Thefollowing 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. References:
• 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

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, 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)

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 standard1. 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 standard1. 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 encapsulation1.
• 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 encapsulation1. The VNI range also does not end at 10000, but at 16777214, which is the maximum possible value for a 24-bit VNI field1.

References:

• VNI Pools (Resources)