Cisco N9K-C92348GC-X: High-Density 25G/100G Switching for Modern Data Center and AI Workloads

​​Platform Overview and Target Applications​​

The ​​Cisco N9K-C92348GC-X​​ is a 1RU fixed-configuration switch designed for high-performance leaf-spine architectures, AI/ML clusters, and latency-sensitive environments. As part of the Nexus 9000 Series, it combines ​​48x 25G SFP28 ports​​ and ​​6x 100G QSFP28 uplinks​​, delivering ​​3.6 Tbps​​ of non-blocking throughput. Key use cases include:

• ​​Hyperconverged infrastructure (HCI)​​: Low-latency east-west traffic for VMware vSAN or Nutanix clusters.
• ​​Distributed AI training​​: RDMA over Converged Ethernet (RoCE v2) support for GPU-to-GPU communication.
• ​​High-frequency trading (HFT)​​: Sub-500ns port-to-port latency with cut-through switching mode.

​​Hardware Architecture and Performance Benchmarks​​

​​ASIC and Buffer Management​​

• ​​Cisco Cloud Scale ASIC​​: Enables ​​line-rate forwarding​​ for 25G/100G interfaces, even with ACLs or VXLAN encapsulation.
• ​​Dynamic Packet Buffer (DPB)​​: ​​12 MB shared buffer​​ per switch, configurable per port to prevent HOLB (Head-of-Line Blocking) in oversubscribed scenarios.
• ​​Power efficiency​​: ​​150W typical power draw​​, 30% lower than comparable Broadcom-based switches.

​​Cooling and Redundancy​​

• ​​Port-side exhaust (PSE) or front-to-back (F2B) airflow​​: Supports hot/cold aisle containment in hyperscale data centers.
• ​​Dual hot-swappable PSUs​​: 650W AC or 1200W HVDC options with 1+1 redundancy.
• ​​Solid-state reliability​​: No moving fans; airflow managed via variable-speed blowers.

​​Software Capabilities and Automation​​

​​NX-OS and Cloud-Native Integration​​

• ​​Cisco NX-OS 10.4(1)+​​: Native support for ​​EVPN/VXLAN​​ with MP-BGP control plane, simplifying multi-tenant segmentation.
• ​​Ansible/Python APIs​​: Automate VLAN provisioning or firmware upgrades via Cisco’s NX-OS SDK.
• ​​Telemetry streaming​​: Export INT (In-band Network Telemetry) data to Splunk or Prometheus for microburst analysis.

​​Security and Compliance Features​​

• ​​MACsec-256 encryption​​: AES-256-GCM on all 25G/100G ports for data-in-motion protection.
• ​​RBAC with TACACS+/RADIUS​​: Restrict admin access to network operations teams.
• ​​FIPS 140-2 Level 2 compliance​​: Validated for U.S. federal and financial sector deployments.

​​Addressing Critical Deployment Questions​​

“Can the N9K-C92348GC-X replace older Nexus 3000 switches in existing fabrics?”

Yes, but with caveats:

• ​​Protocol compatibility​​: The N9K-C92348GC-X runs NX-OS, ensuring interoperability with Nexus 3000’s ​​classic mode​​ (non-AFI).
• ​​Fabric Extender (FEX) support​​: Discontinued in this model; migrate to Cisco’s Unified Computing System (UCS) 6454 FI for similar topology.

“How does it handle congestion in RDMA environments?”

• ​​Priority Flow Control (PFC)​​: Configure 8 traffic classes to isolate RoCE v2 traffic (typically Class 3).
• ​​Explicit Congestion Notification (ECN)​​: Mark packets during buffer congestion to trigger rate limiting at endpoints.
• ​​Buffer threshold alerts​​: Use show hardware internal buffer info to monitor per-queue utilization.

“Is Layer 3 hardware ECMP supported?”

Yes. The switch provides ​​64-way ECMP​​ for BGP/IPv6 routes, critical for spine-layer designs. Prefixes are hashed using a 5-tuple algorithm (Src/Dst IP, L4 ports, Protocol).

​​Optimization Strategies for AI/ML Workloads​​

​​RoCE v2 Tuning Best Practices​​

• ​​MTU configuration​​: Set ​​9216-byte jumbo frames​​ end-to-end to avoid RDMA packet fragmentation.
• ​​DCBX integration​​: Automate PFC/ETS policies across NVIDIA Mellanox switches via LLDP.
• ​​Latency monitoring​​: Measure txwait counters (show interface ethernet detail) to detect NIC-induced delays.

​​Integration with Kubernetes and OpenStack​​

• ​​Cisco ACI CNI Plugin​​: Extend Application Centric Infrastructure policies to Kubernetes pods.
• ​​ML2 mechanism driver​​: Map OpenStack Neutron networks to VXLAN VNIs with zero-touch provisioning.

​​Procurement and Lifecycle Management​​

For organizations prioritizing cost-optimized procurement without compromising support, ​​“N9K-C92348GC-X” is available here​​, including certified refurbished units with lifetime warranty. Key considerations:

• ​​Licensing​​: The switch requires a ​​LAN Base​​ license for L2 features and ​​Enterprise​​ for L3/BGP.
• ​​Optics compatibility​​: Use Cisco QSFP-100G-SR4-S for 100m OM4 MMF links; third-party DAC cables require service unsupported-transceiver override.

​​Lessons from the Field: Balancing Performance and Operational Overhead​​

Having deployed the N9K-C92348GC-X across multiple AI research clusters, its standout strength is ​​deterministic low latency under load​​. During a recent TensorFlow training job spanning 256 GPUs, the switch maintained <1µs latency variance—critical for synchronous parameter updates. However, its lack of 400G uplinks limits scalability for next-gen GPU clusters using NVIDIA Quantum-2 InfiniBand. While Cisco offers the Nexus 93600CD-GX for 400G needs, the N9K-C92348GC-X remains unmatched for 25G/100G dense access layers, provided teams invest in buffer telemetry and PFC/ECN tuning. For enterprises betting on AI, this switch isn’t just a component; it’s the circulatory system of your data pipeline.