Cisco ACI Training

Understand why VXLAN was introduced and what problems it solves Build strong foundation for overlay networking Legacy Data Center Limitations a) VLAN scalability (4094 limit) b) STP drawbacks c) MAC table explosion d) Suboptimal traffic paths VXLAN Architecture a) Overlay vs physical underlay b) Role of IP fabric c) Control plane vs data plane VXLAN Header Breakdown a) Outer Ethernet b) Outer IP (src/dst = VTEPs) c) UDP (port 4789) d) VXLAN header (VNI field) VNI (16M Segments) a) 24‑bit VNI space b) VLAN‑to‑VNI comparison c) Tenant isolation using VNIs Underlay vs Overlay a) Underlay: IP reachability, ECMP b) Overlay: tenant traffic encapsulation MTU & VTEP Basics a) VXLAN encapsulation overhead b) Jumbo MTU requirement (≥ 1550) c) VTEP roles: source & destination Key Takeaway VXLAN decouples logical networks from physical topology and enables massive scale.

Spine–Leaf Architecture a) Clos fabric principles (Leaf/Spine design) b) ECMP forwarding c) No STP requirement NVE Interface a) Network Virtualization Edge b) VXLAN termination point VLAN–VNI Mapping a) Local VLAN to VXLAN segment b) Bridge‑Domain behavior Static Ingress Replication a) Head‑end replication b) Flooding to all remote VTEPs c) Scalability drawbacks BUM Packet Walk a) Broadcast frame encapsulation b) Replication across fabric c) De-capsulation at remote VTEPs Key Takeaway Static VXLAN works but does not scale well due to flood‑and‑learn behavior.

Eliminate flooding using MP‑BGP EVPN Understand EVPN route types MP‑BGP EVPN Introduction a) Address Family EVPN b) Control‑plane driven VXLAN EVPN Route Types a) Route Type 2 – MAC/IP Advertisement b) Route Type 3 – Inclusive Multicast Ethernet Tag Control‑Plane MAC Learning a) MAC learning via BGP b) No data‑plane learning ARP Suppression a) Distributed Anycast gateway b) ARP reply using EVPN database EVPN Packet Walk a) Unicast traffic flow b) MAC lookup → VTEP resolution → encapsulation Key Takeaway EVPN converts VXLAN into a highly scalable, control‑plane driven solution.

Enable inter‑subnet routing in VXLAN fabric Understand endpoint mobility VRF & L3 VNI a) VRF segmentation b) L3 VNI for routing between BDs Symmetric IRB a) Routing at ingress and egress b) Optimal traffic forwarding Inter‑Subnet Packet Walk a) Same leaf vs remote leaf routing b) Role of L3 VNI Silent Host Behavior a) Host without initial traffic b) Control‑plane learning Endpoint Mobility a) MAC move detection b) Sequence numbers c) Convergence behavior Key Takeaway L3 VXLAN enables scalable multi‑tenant routing with seamless mobility.

Understand ACI building blocks See how ACI uses VXLAN internally ACI Fabric Components a) Spine, Leaf, APIC Underlay & Overlay Underlay: IS‑IS routing Overlay: VXLAN APIC Roles a) Policy controller b) Central management & automation Fabric Discovery a) Zero‑touch provisioning b) Node role assignment Key Takeaway ACI automates VXLAN fabric using a centralized policy model.

Learn logical constructs used in ACI Tenant / VRF / Bridge Domain a) Logical segmentation b) BD vs VLAN comparison Application Profiles & EPGs a) Endpoint grouping b) Static & dynamic endpoints Contracts & Filters a) Whitelist security model b) Subject, filter, contract flow Key Takeaway ACI focuses on intent instead of configuration.

Understand how ACI forwards traffic internally COOP Learning a) Council of Oracle Protocol b) Distributed endpoint database Proxy ARP a) Reduced flooding b) Fast endpoint resolution Intra‑EPG Traffic a) No contracts required Inter‑EPG Traffic a) Contract enforcement Policy CAM a) TCAM programming based on policy Key Takeaway ACI forwarding is VXLAN‑based with integrated security enforcement.

Configure access layer connectivity Interface Policies a) Speed, CDP, LLDP, LACP AEP & Domains a) Physical, VMM, L3 domains vPC inside ACI a) vPC pairs b) Dual‑homed endpoints Key Takeaway Access policies bind physical infrastructure with logical policy.

Connect ACI fabric with external networks L2Out a) VLAN extension b) Legacy network integration L3Out a) OSPF / BGP / Static routing External EPG a) External endpoint classification Route Control a) Import/export policies b) Contract enforcement Key Takeaway ACI provides policy‑controlled north‑south connectivity.

Integrate virtualization & multi‑site ACI APIC ↔ VMware Integration a) VCenter registration b) VDS automation EPG ↔ Portgroup Mapping a) Dynamic VM attachment Endpoint Mobility a) VM vMotion behavior ACI Anywhere a) Multi‑site b) Cloud ACI c) Stretched policy model Final Takeaway ACI abstracts VXLAN complexity and delivers policy‑driven, scalable data centers. End Result: After training, learners can confidently design, deploy, analyze packet flow, and troubleshoot VXLAN EVPN & Cisco ACI fabrics.