Networking and Datacenter Fabric Architecture

Canonical hub for network architecture scope, decision authority, and evidence-linked defaults.

Scope

In scope

• Domain operating model and rollout lanes: topic-datacenter-3-0, topic-network-aci-location-a-ai-fasttrack.
• Location B implementation profile and runbooks: topic-network-nxos-evpn-implementation.
• OpenShift and EVPN production contract: openshift-evpn-production-target-baseline.
• Addressing policy and test gates: network-addressing-guardrails, topic-network-addressing-policy-test-matrix.
• 1H2026 delivery scope: WP-01 DC3.0 Network and Supporting Services.

Out of scope

• Cable-level design and optics procurement beyond architecture constraints.

Key Concepts

• Accepted baseline
• Rollout model is lane-scoped by adr-019-hybrid-network-rollout-aci-a-ai-only-evpn-b-target: Location A ACI for AI-only scope, Location B EVPN/VXLAN target lane.
• Deployment model uses generated artifacts plus full replace per adr-002-nxos-config-replace and validation gates per adr-018-network-validation-ansible-vendor-cli.
• 1H2026 addressing baseline remains adr-007-ip-addressing-2026 with enforcement in network-addressing-guardrails.

• Interim defaults while draft ADRs are open
• Service and transport are treated as separate layers per the working direction in adr-020-backbone-service-vs-transport-l3vpn-sr-mpls.
• DC-to-backbone default is L3 handoff with L2 stretch as exception path per adr-021-dc-evpn-to-backbone-l3vpn-interconnect.
• Forward IPv6 scale model follows adr-023-ipv6-numberplan-and-cluster-scale-strategy until accepted.

• Where details live
• OpenShift plus EVPN baseline contract: openshift-evpn-production-target-baseline.
• Implementation mechanics and runbooks: topic-network-nxos-evpn-implementation.
• Addressing behavior, sizing, and test evidence: topic-network-ip-addressing-scale-and-vrf-model, topic-network-addressing-policy-test-matrix.

Related Decisions (ADRs)

• ADR-019 Hybrid rollout: ACI in Location A (AI-only), EVPN/VXLAN in Location B (target) (accepted)
• ADR-021 DC EVPN to Backbone L3VPN interconnect pattern (draft)
• ADR-020 Backbone service-vs-transport model (draft)
• ADR-016 Network topology for 2026 (superseded) (superseded)
• ADR-002 NX-OS configuration replace (accepted)
• ADR-018 Network validation baseline (Ansible plus vendor CLIs) (accepted)
• ADR-003 Network validation tooling (superseded) (superseded)
• ADR-007 IP addressing plan (accepted)
• ADR-023 IPv6 numberplan and cluster scale strategy (draft)
• ADR-008 Storage network segmentation (accepted)

Supporting Facts

• Fabric building blocks: DC Network Structure, DC Network Structure, automation.
• Primary implementations: Cisco Nexus 9000, Cisco NX-OS, NetBox.
• Cross-domain controls: Automation, Public Key Infrastructure, Automation.

Key Sources

• NX-OS configure-replace vendor reference
• Cisco NX-OS Ansible best-practices summary
• OVN-Kubernetes OKEP-5088 EVPN summary
• OpenShift multiple networks VRF summary
• OpenShift real-routing and NAT-free path summary
• Cisco NX-OS EVPN ESI multi-homing summary
• Logius overheidsbreed IPv6-nummerplankader summary

Diagrams

• Implementation dependency and sequencing view: WP-01 DC3.0 Network and Supporting Services.

Mapping Views

• DC 3.0 capability-to-solution mapping for this domain: DC 3.0 Building Block Lens.

Next Steps

1. Promote adr-020-backbone-service-vs-transport-l3vpn-sr-mpls and adr-021-dc-evpn-to-backbone-l3vpn-interconnect from draft to accepted using the evidence gates in topic-network-nxos-evpn-implementation.
2. Promote adr-023-ipv6-numberplan-and-cluster-scale-strategy after NetBox profile and CI evidence closes in topic-network-addressing-policy-test-matrix.
3. Keep contract notes (openshift-evpn-production-target-baseline, network-addressing-guardrails) aligned with ADR status and workpackage acceptance in WP-01.