The statement accurately describes a common and valid Data Center Interconnect (DCI) architecture for campus environments using Aruba VSX technology. A VSX Link Aggregation Group (LAG) can be established between two distinct VSX pairs, with one pair in each data center. This configuration creates a resilient, high-bandwidth, loop-free Layer 2 path between the data centers. This path functions as a trunk, enabling the seamless extension of VLANs and their corresponding broadcast domains across the two physical sites, which is a primary goal of L2 DCI.

This is a "True or False" question. The statement is factually correct according to official Aruba design principles. The alternative, "False," would be incorrect because this topology is a standard, supported, and relatively straightforward method for achieving Layer 2 DCI in a campus setting with Aruba CX switches. It leverages the core capabilities of VSX to provide multi-chassis redundancy for the interconnect link itself.

1. Aruba Validated Solution Guide: Data Center Interconnect with Aruba CX Switches (April 2021). This guide explicitly details the architecture described in the question.

Page 7

"Layer 2 DCI" section: "A simple solution for campus data centers is to extend the L2 domains between the two locations. This can be achieved by creating a VSX LAG between the pairs of VSX switches." The guide includes a diagram (Figure 3) illustrating this exact topology

labeling it as "VSX LAG for L2 DCI."

2. ArubaOS-CX VSX Configuration Guide for CX 10.12 (Part Number: 5200-8318a

Edition: 1). This official vendor documentation describes the capabilities of VSX LAGs.

Chapter: "VSX LAGs

" Section: "Interconnecting two VSX pairs with a VSX LAG": This section states

"A VSX LAG can be configured between two different VSX pairs. This configuration is useful in a data center environment where a pair of VSX switches are in one rack and another pair of VSX switches are in another rack." This confirms that the fundamental technology for connecting two separate VSX clusters via a VSX LAG is a supported feature.

In an Aruba CX EVPN-VXLAN fabric, an underlay routing protocol is required to provide IP reachability between the Virtual Tunnel Endpoints (VTEPs), which are typically the leaf switches. OSPF is the recommended and most commonly deployed Interior Gateway Protocol (IGP) for this purpose within a single data center fabric (referred to as a "room" in the scenario). It is a robust, standards-based, and well-understood link-state protocol that efficiently establishes the necessary underlay connectivity for the VXLAN overlay to function. The design ensures that all VTEP loopback addresses are reachable across the fabric.

A. iBGP: iBGP is used for the EVPN overlay control plane to exchange MAC/IP address information between VTEPs within the same Autonomous System, not for underlay reachability.

B. eBGP: While eBGP can be used as an underlay protocol (a "BGP-as-underlay" design), OSPF is the more common and standard IGP choice for a single Aruba CX fabric.

D. IS-IS: IS-IS is a valid link-state protocol for an underlay, but it is less commonly used and documented in Aruba enterprise data center designs compared to OSPF.

1. ArubaOS-CX 10.11 EVPN-VXLAN Guide

Hewlett Packard Enterprise Development LP

(2023). In the "Configuring the underlay" section

the guide states

"The underlay network uses a routing protocol

such as OSPF

to provide unicast routing of traffic between VTEPs." The subsequent configuration examples exclusively use OSPF for the underlay. (Page 16).

2. HPE Aruba Networking Validated Solution Guide - Data Center Networking with EVPN-VXLAN

Hewlett Packard Enterprise Development LP

(2022). In the chapter on "Underlay Network Design

" the guide specifies

"An Interior Gateway Protocol (IGP) is required to provide reachability between VTEPs in the underlay network. OSPF is a common choice for the IGP in a spine-and-leaf fabric." (Section: Underlay Routing).

Ethernet Ring Protection Switching (ERPS), defined by the ITU-T G.8032 standard, is specifically designed for resilient ring topologies commonly found in Metropolitan Area Networks (MAN) or carrier networks. This makes it highly suitable for interconnecting geographically separate data centers. ERPS provides rapid convergence times (sub-50ms), ensuring high availability for the Layer 2 DCI link. When combined with the Virtual Router Redundancy Protocol (VRRP), it creates a complete solution that offers both a resilient Layer 2 path and a redundant Layer 3 default gateway for workloads across the data centers.

A. VSX (Virtual Switching Extension) can be used for DCI but has strict low-latency requirements for its Inter-Switch Link (ISL), which may not be met over longer geographical distances.

C. STP (Spanning Tree Protocol) is a legacy protocol with slow convergence times (30-50 seconds), making it unsuitable for modern DCI applications that demand near-instantaneous failover.

D. VSF (Virtual Switching Framework) is a switch stacking technology intended for switches in the same physical location, such as a single rack or wiring closet, and cannot span separate buildings.

1. ArubaOS-CX 10.11 Layer 2 Bridging Guide

Chapter: "Ethernet Ring Protection Switching (ERPS)"

Page 1.

Quote/Paraphrase: "ERPS provides sub-50 ms protection and recovery switching for Ethernet traffic in a ring topology and ensures that there are no loops formed at the Ethernet layer. ERPS is often used in carrier and metro Ethernet networks..." This document confirms ERPS is designed for the exact use case of interconnecting sites over a metro/carrier network with fast failover.

2. ArubaOS-CX 10.11 Virtual Switching Extension (VSX) Guide

Chapter: "VSX deployment considerations"

Section: "VSX split-brain detection".

Quote/Paraphrase: While not giving a hard number

the guide emphasizes the need for a low-latency

high-bandwidth ISL. Industry best practices for stretched clustering technologies like VSX typically recommend a round-trip time (RTT) of less than 10ms

which limits its geographical scope compared to carrier-grade protocols like ERPS.

3. Aruba Design Principles and Methodologies Guide

Chapter 2: "Aruba Campus for Midsize Networks"

Section: "Switching architecture".

Quote/Paraphrase: This guide differentiates VSF and VSX. It describes VSF as a technology for creating a single logical device from a stack of access switches

implying co-location. It positions VSX for the aggregation/core layer for high availability within a site. This context makes VSF clearly unsuitable for DCI between buildings.

Assumptions are critical components of a solution design document that address gaps in information or clarify the conditions under which the design is considered valid. Since each project has a unique scope, customer environment, set of technical requirements, and business objectives, the assumptions made during the design process must be tailored to that specific context. For instance, assumptions regarding available power and cooling in network closets, the state of existing cabling infrastructure, or client device capabilities will inherently differ from one project to another, making them project-dependent.

A. Assumptions are essential for defining the project's scope and boundaries; excluding them from a proposal creates significant risk and ambiguity.

B. While including assumptions is a critical best practice, this statement is an absolute; a very simple, fully-defined project might not require a separate assumptions list.

C. Proactively documenting assumptions is a core responsibility of the solution architect to ensure clarity; it is not a reactive task performed only upon request.

1. HPE Education Services

Designing Aruba Solutions

Rev 20.11 Courseware. The course

which prepares for the HPE7-A04 exam

emphasizes the initial "Information Gathering" phase. This phase involves analyzing a customer's specific business and technical requirements

which often reveals unknowns. Documenting assumptions is the standard process for addressing these unknowns

which are unique to each customer engagement. (Module: "Gathering and Analyzing Customer Information").

2. Aruba Networks

Aruba Validated Solution Guides (VSG). Each VSG

such as the "Aruba Campus for Midsize Networks VSG

" is built upon a specific set of assumptions regarding scale

applications

and existing infrastructure pertinent to a particular use case. This demonstrates that a design for a different use case (e.g.

a large enterprise or a hospital) would be based on a different set of assumptions

confirming their project-specific nature. (Refer to the "Planning and Design" section of any Aruba VSG).

3. MIT OpenCourseWare

16.842 Fundamentals of Systems Engineering

Fall 2015. Lecture 3

"Identifying Stakeholder Needs

" covers the process of defining a system's operational context and requirements. This process necessitates making and documenting assumptions to handle incomplete or ambiguous information provided by stakeholders. These assumptions are

by definition

specific to the system and project being developed.

The End-of-Row (EoR) or Middle-of-Row (MoR) architecture consolidates network switching for a row of racks into a single, large chassis-based switch. A primary disadvantage is the cabling infrastructure; every server requires a dedicated, long cable run to the central switch. This results in extensive, complex, and difficult-to-manage cabling bundles that can impede airflow and increase costs.

Additionally, the EoR/MoR model is often considered less scalable than alternatives like Top-of-Rack (ToR). It follows a "scale-up" model, requiring a significant upfront investment in a large chassis. Once the port capacity of this chassis is reached, expansion becomes a major, disruptive, and expensive project, unlike the incremental "scale-out" approach of ToR designs.

A. More equipment: This is incorrect. The EoR/MoR design consolidates switching into fewer, larger devices compared to the Top-of-Rack (ToR) model, which uses many smaller switches.

B. Higher latency for rack-to-rack traffic within the row: This is incorrect. EoR/MoR provides lower latency for this specific traffic path, as communication between servers in different racks within the same row is a single hop through the central switch.

1. Aruba Data Center Network Design for Aruba CX Switching

Version 1.0 (March 2021)

Page 11

Table 1 "Comparison of ToR

MoR

and EoR designs": This table explicitly details the disadvantages of EoR/MoR. For "Cabling

" it states

"Requires structured cabling system. Can result in a large amount of cabling." This directly supports option C. For "Scalability

" it notes

"Requires large upfront investment. Can result in unused ports

" which supports the "less scalable" aspect of option D.

2. HPE FlexFabric Cookbook

Version 2.11 (December 2016)

Page 21

Section "End-of-Row": The document describes EoR

stating

"The main disadvantage of this model is the large amount of cabling required between the server racks and the EoR switches." This validates option C. It also implies scalability issues by contrasting it with the flexibility of other models.