Dell PowerSwitch Z9432F-ON 400GbE Switch

The Dell PowerSwitch Z9432F-ON is a 1RU aggregation switch with 32 ports of 400GbE in QSFP56-DD form factor plus two 10GbE SFP+ ports, a 25.6 Tbps full-duplex switch fabric, 5.2 Bpps of forwarding capacity, a 132MB packet buffer and sub-850 ns latency. This unit is the reverse-airflow build.

Dell lists the Z9432F-ON under both its AI switches and its data centre switches categories, and that dual classification is the honest description of what this box is: a general-purpose 400GbE aggregation switch that happens to have the buffer and the RDMA support that AI and machine-learning fabrics demand.

Thirty-two 400GbE ports in one rack unit

The headline configuration is 32 ports of 400GbE. Dell also publishes the two densities that matter more in practice: up to 128 ports of 100GbE, or up to 144 ports of 10, 25 or 50GbE, both reached with breakout cables. One rack unit, and a choice between a 400GbE spine and a 128-port 100GbE aggregation layer.

Every 400GbE port is multi-rate. Dell states it explicitly: the 400GbE ports support 10/25/40/50/100GbE, and 40GbE ports support 10 and 40GbE. That is what makes this switch buildable into an existing estate rather than only into a greenfield one - the same cage that will carry a 400GbE link next year can carry a 100GbE link today.

Two 10GbE SFP+ ports sit alongside, useful for management uplinks or out-of-band paths that should not consume a 400GbE cage.

The buffer is the specification that matters

At 132MB, the packet buffer on this switch is several times what the previous 100GbE generation carried, and it is the single most consequential number on the sheet. Aggregation points are where incast happens - many senders converging on one receiver, all at line rate - and buffer is what absorbs it. A switch with a large fabric and a small buffer will drop under exactly the traffic pattern that aggregation exists to handle.

That is also why this design shows up in AI fabric conversations. Distributed training traffic is synchronised and bursty by construction: every node finishes its step at roughly the same moment and every node transmits at roughly the same moment. Routable RoCE support lets that traffic run RDMA over a routed fabric, and Data Center Bridging - priority flow control under 802.1Qbb, enhanced transmission selection under 802.1Qaz, DCBx and iSCSI TLV - gives it the lossless treatment it needs. Buffer, RoCE and DCB together are why Dell files this switch under AI as well as data centre.

Latency is sub-850 ns and the fabric is 25.6 Tbps full duplex, delivering line-rate performance under full load. Table scale runs to 156K MAC addresses, up to 400K IPv4 routes with ALPM, 300K IPv6 routes and 4K Layer 2 VLANs, with 64 MSTP instances.

QSFP56-DD, and what the cage actually is

QSFP56-DD is a double-density QSFP cage: eight lanes of 50G PAM4 rather than the four lanes of a QSFP28. That is where 400GbE comes from, and it is also why the same cage breaks out so flexibly - eight lanes can be divided several ways.

Two practical consequences. First, optics for these ports are 400GbE-class modules; a QSFP28 100GbE module is a different cage generation and does not simply drop in as a 400GbE link. Second, optics power is a real constraint at this density: Dell budgets up to 15W per module across all QSFP56-DD ports, with an allowance for four ports at 20W when the switch is running in the I/O-panel-to-PSU airflow direction. If you are planning long-reach coherent modules, check their power draw against that budget before you order.

Airflow: standard and reverse builds

This listing is the model page for the Z9432F-ON and covers both airflow builds. Select the direction under the Airflow option: direction is set by the power supplies and fan modules fitted, so it is a build-time choice, and PSUs and fans must both face the same way.

The reverse-airflow unit: air is drawn in at the power-supply face and exhausted at the I/O panel. That is the direction you want when the switch is racked with its ports facing the hot aisle - the common layout, because it puts the switch ports on the same side as the server NICs. Power supplies and fan modules are direction-specific parts, so the whole chassis runs one direction and changing it later means replacing all of them. Seven fans provide 6+1 redundancy.

The power detail worth reading twice is Dell's own footnote on redundancy. The switch takes two hot-swappable power supplies at 1+1 redundancy - except when running on lowline power. A 100-127 VAC supply is explicitly a non-redundant solution on this model. If your rack is on 120V and you were counting on PSU redundancy, that assumption does not hold; plan for 200-240 VAC. Maximum consumption is 1404W with a 900W typical figure.

SmartFabric OS10, SONiC, and buying it second-hand

The "-ON" suffix is Dell's open networking designation. The switch supports the open source Open Network Install Environment for zero-touch installation of Dell SmartFabric OS10, Enterprise SONiC Distribution by Dell Technologies, or an alternative ONIE-compatible network operating system.

On the secondary market that separation is the whole point. The hardware you buy is 32 ports of 400GbE silicon, an 8-core Denverton control plane with 32GB of DDR4 ECC and a programmable NPU pipeline. The operating system is a separate decision made at install time, not a licence state inherited from a previous owner. Expect a unit to need an OS install on arrival - a switch sitting at the ONIE prompt is in the state Dell designed.

Rack mounting uses Dell's accelerated mounting kits. Note that the Z9432F-ON does not take the universal S-series rail; it shares a dedicated 1U ReadyRails kit with the S5448F-ON.

Where it sits in Dell's 400GbE line

The Z9432F-ON is the entry point to 400GbE in Dell's fixed-format range, and it is the 1RU one. The Z9664F-ON doubles the port count to 64 x 400GbE and the fabric to 51.2 Tbps, in 2RU. The Z9864F-ON moves to 800GbE on OSFP112 cages and is the switch Dell positions for large AI training clusters. Below all three, the Z9264F-ON and Z9100-ON hold the 100GbE tier.

Every unit is professionally reconditioned, fully tested and shipped with warranty. This model is quote-only - tell us the airflow direction, optics and quantity you need and a specialist will come back to you with availability.

Specifications