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14.3 Creating a Low-Level Design

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HPE Aruba Networking Certified Associate - Campus Access HPE6-A85

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1 Introduction: HPE6-A85 Exam Overview

HPE6-A85 Exam Facts and Current Blueprint

2 Chapter 1: Network Stack Fundamentals

1.1 OSI Reference Model and Encapsulation 1.2 TCP/IP Protocol Suite and IP Headers 1.3 Layer 2 Operation, ARP, and 802.1Q Tagging

3 Chapter 2: Physical Connectivity and Host Addressing

2.1 Ethernet Media and Transceiver Standards 2.2 Power over Ethernet (PoE, PoE+, PoE++) Standards and Budgeting 2.3 LLDP, LLDP-MED, and Voice VLAN Configuration 2.4 Host IP Addressing and DHCP Relay Operations

4 Chapter 3: Network Resiliency and Virtualization

3.1 Virtual Switching Framework (VSF) Architecture and Topologies 3.2 VSF Split Detection, Failover, and Auto-Stacking 3.3 Virtual Switching Extension (VSX) Architecture and Operations 3.4 High-Availability Gateways: VRRP and VSX Active-Gateway

5 Chapter 4: AOS-CX Architecture and Switch Operation

4.1 AOS-CX Hardware Portfolio and State Database Architecture 4.2 Network Analytics Engine (NAE) and Automated Telemetry 4.3 AOS-CX Interface Configuration and Port Control 4.4 Link Aggregation (LAG) and LACP Configuration

6 Chapter 5: Layer 2 Protocols and Spanning Tree

5.1 AOS-CX VLAN Configuration and Native VLAN Handling 5.2 Spanning Tree Protocols: STP, RSTP, and MSTP 5.3 Spanning Tree Protections and Loop Prevention 5.4 MAC Address Table Learning, Aging, and Forwarding

7 Chapter 6: Wireless Fundamentals, Standards, and RF

6.1 IEEE 802.11 Standards and Wi-Fi Generations 6.2 RF Fundamentals, Signal Propagation, and Channel Design 6.3 Aruba Access Point Hardware Portfolio and Suffix Conventions 6.4 WLAN Topologies, BSSID/ESSID, and Roaming Standards

8 Chapter 7: Aruba Wireless Architecture and Management

7.1 AOS 10 Architecture and Aruba Central Integration 7.2 Wireless Forwarding Modes: Bridge vs Tunnel Mode 7.3 Automated RF and Client Optimization: AirMatch and ClientMatch 7.4 Secure Wireless Access: WPA3, SAE, and MPSK Implementation

9 Chapter 8: IP Routing Fundamentals and OSPF

8.1 IP Routing Principles and Packet Forwarding 8.2 OSPFv2 Protocol Mechanics and Adjacency Formation 8.3 OSPF Designated Routers and Multi-Area Deployments 8.4 ECMP, Static Routing, and VRF Isolation

10 Chapter 9: Campus Network Security and Segmentation

9.1 DHCP Snooping and Dynamic ARP Inspection 9.2 Port Security and MAC Address Limiting 9.3 ClearPass Policy Management and RADIUS Change of Authorization 9.4 Dynamic Segmentation, User-Based Tunneling, and Policy Enforcement

11 Chapter 10: Authentication, Authorization, and Accounting

10.1 The AAA Framework and Architecture 10.2 802.1X Authentication and EAP Methods 10.3 MAC Authentication and Captive Portal Onboarding 10.4 Administrative Access Control: RADIUS vs TACACS+

12 Chapter 11: Network Management and Telemetry

11.1 Aruba Central Cloud Architecture and Group Configuration 11.2 Zero-Touch Provisioning (ZTP) and Aruba Activate 11.3 AI Insights and Aruba User Experience Insight (UXI) 11.4 Network Telemetry, Streaming APIs, and SNMP/Syslog

13 Chapter 12: Troubleshooting the Solution

12.1 Structured Troubleshooting Methodologies and Scope Isolation 12.2 AOS-CX Layer 2 and Interface Diagnostic Commands 12.3 Layer 3, IP Services, and End-to-End Diagnostics 12.4 Physical-Layer Troubleshooting 12.5 Troubleshooting Wireless Clients and Network Access

14 Chapter 13: Optimizing Performance: QoS, Baselines, and Comparisons

13.1 Quality of Service (QoS) Classification and Marking 13.2 Queuing Algorithms and Congestion Management 13.3 Traffic Policing, Shaping, and Broadcast Rate Limiting 13.4 Establishing a Performance Baseline 13.5 Comparing Results to the Baseline

15 Chapter 14: Plan the Solution

14.1 Analyzing the Current Environment 14.2 Interpreting an Architect's High-Level Design 14.3 Creating a Low-Level Design 14.4 Preparing for Implementation

16 Chapter 15: Validate and Operate the Solution

15.1 Validating the Solution 15.2 Performing Firmware Updates 15.3 Making Basic Ongoing Configuration Changes 15.4 Maintaining Network Documentation

14.3 Creating a Low-Level Design

Key Takeaways Explain This Topic AI

A low-level design (LLD) turns the HLD into device-level detail: hardware and optics, port maps, VLAN and IP tables, protocol parameters, wireless profiles, and management settings.

Port maps record every interface's purpose, VLAN mode, PoE priority, and authentication settings so configuration and documentation come from the same source.

AOS-CX values belong in the LLD in AOS-CX form: spanning tree priority as a 0-15 multiplier, rate limits in pps or percent, and LAG hash l3-src-dst unless a different hash is required.

Wireless LLD entries map each SSID to security, forwarding mode, VLAN or gateway cluster, and role, plus RF guidance such as 20 MHz channels in 2.4 GHz.

Central templates use variables such as hostnames and management IP addresses, with one variable-file row per device, so the LLD's tables can feed provisioning directly.

Last updated: October 2026

14.3 Creating a Low-Level Design

Quick Summary: A low-level design (LLD) is the implementation blueprint. Where the HLD says "each floor gets a VSF stack," the LLD says which models, which ports form VSF links, which ports uplink to which core ports, which VLAN each access port uses, what the management IP of each stack is, and which SSIDs use which security and forwarding mode. HPE6-A85 lists "create a low-level design" as a Plan objective, so expect questions about what belongs in an LLD and how its values are expressed on AOS-CX.

  • What the LLD Contains
  • 1. Hardware Bill of Materials

Switch models per closet , sized from the environment analysis: port count, PoE budget and class (Section 2.2), Smart Rate ports for multi-gigabit APs, and uplink speeds.

Stacking: CX 6300 stacks of up to 10 members or CX 6200F stacks of up to 8 (Section 3.1).

Optics and cables: transceivers matched to fiber type and distance (Section 2.1), DACs for short in-rack links, and spares.

Access points per area: model chosen from coverage and capacity needs, form factor (indoor, external-antenna, outdoor, hospitality), and power class (Section 6.3).

Power: power supplies and redundancy for each switch.

2. Physical Layout and Port Maps

A port map assigns every interface a purpose:

  • Switch Port Connected device Mode VLAN(s) PoE priority Access control
  • FL2-STACK 1/1/1-1/1/40 Desks (phone + PC) Trunk, native data 10 untagged, 20 voice high 802.1X + MAC-Auth
  • FL2-STACK 1/1/41-1/1/46 APs Trunk 100 AP mgmt (native), 500 guest critical MAC-Auth for APs
  • FL2-STACK 1/1/49-1/1/50 VSF link 1/2 VSF n/a n/a n/a

FL2-STACK 1/1/52, 2/1/52 Core VSX pair LAG 1 (LACP) 10,20,30,100,500,999 (native 999) n/a Trusted (DHCP snooping, ARP inspection)

Using the same port map for configuration and documentation prevents the classic mismatch where the drawing says one thing and the switch does another.

3. VLAN and IP Tables

  • VLAN Name Subnet Gateway (active-gateway VIP) DHCP helper Notes
  • 10 USERS 10.10.0.0/22 10.10.0.1 10.1.100.50 DHCP snooping, ARP inspection
  • 20 VOICE 10.20.0.0/23 10.20.0.1 10.1.100.50 voice VLAN, DSCP trusted from phones
  • 30 IOT 10.30.0.0/23 10.30.0.1 10.1.100.50 MAC-Auth or MPSK
  • 100 AP-MGMT 10.100.0.0/24 10.100.0.1 10.1.100.50 AP management
  • 500 GUEST 172.16.0.0/22 firewall firewall Bridged guest SSID
  • 999 NATIVE-UNUSED none none none Trunk native VLAN only

Also record management addresses per device, loopbacks and OSPF router IDs, point-to-point link subnets (/30 or /31), and the management VRF and gateway.

4. Protocol Parameters in AOS-CX Terms

Spanning tree: region name, revision, VLAN-to-instance mapping, and root priorities expressed as AOS-CX multipliers ( spanning-tree priority 0 for the primary root, 1 for the secondary; Section 5.2).

LAGs: LACP active on both ends, member ports on different stack members, and hash ( l3-src-dst is the default).

VSF/VSX: secondary member, split-detection cabling, ISL ports, keepalive addresses, and active-gateway virtual MACs.

OSPF: areas, router IDs, point-to-point network type on routed uplinks, and passive SVIs.

Security: which ports are trusted for DHCP snooping and ARP inspection; port-security client limits; protection features such as BPDU guard and loop protection on edge ports.

QoS: trust mode per port type and any queue or schedule profiles.

5. Wireless Design Details

  • SSID Security Forwarding VLAN / destination Role Bands
  • CORP WPA3-Enterprise (802.1X via ClearPass) Tunnel Gateway cluster VLAN 40 Employee 5 GHz, 6 GHz
  • VOICE WPA3-Enterprise, 802.11r enabled Tunnel Gateway cluster VLAN 41 Voice 5 GHz
  • IOT MPSK Bridge VLAN 30 Per-device role 2.4 GHz, 5 GHz
  • GUEST Enhanced Open (OWE) or captive portal Bridge VLAN 500 Guest 2.4, 5, 6 GHz (OWE required in 6 GHz)

Add RF guidance consistent with Section 6.2: 20 MHz channels in 2.4 GHz, 20 or 40 MHz in dense 5 GHz areas, and wider channels only where the 6 GHz channel pool allows. AirMatch will tune channels and power, but the LLD should state constraints and AP placement.

6. Management and Provisioning

Central structure: Classic Central groups and sites, or new Central scopes (site collections, sites, device groups), plus which device lands where (Section 11.1).

Templates and variables: a Classic Central template group uses variables such as hostname and management IP, filled in from a variable file with one row per device. LLD tables are the natural source for that file.

Firmware target: the AOS-CX and AOS 10 versions to run, from the release notes.

Naming conventions: for example building-floor-role-number, used consistently for hostnames, LAG descriptions, and labels.

Quality Checks Before Sign-Off

Every HLD requirement maps to at least one LLD entry.

Every port in the port map has a VLAN mode and an access-control decision.

Every VLAN has a gateway, DHCP behavior, and a reason to exist on each trunk that carries it.

PoE totals per switch fit the budget with the chosen allocation method.

Native VLANs are listed in the trunks' allowed lists where they are meant to carry traffic (an AOS-CX requirement).

The architect has reviewed and approved the LLD.

Common Exam Traps

Writing generic values that AOS-CX will reject. For example, an STP priority of 4096 must be entered as the multiplier 1 .

Leaving out the management plane. Management VLAN or VRF, gateways, NTP, DNS, and Central placement are part of the LLD.

Mixing up HLD and LLD. "Use VSX at the core" is HLD; "ISL is LAG 256 on ports 1/1/53-1/1/54" is LLD.