Dell PowerSwitch S5296F-ON 25GbE Switch

The Dell PowerSwitch S5296F-ON is a 2RU, 96-port 25GbE SFP28 switch with eight 100GbE QSFP28 uplinks, a 3.2 Tbps switching fabric (6.4 Tbps full duplex) and 850 nanosecond port-to-port latency. It is the highest-density member of the S5200-ON family and the only one that is not 1RU.

Dell built it for middle-of-row and end-of-row aggregation rather than classic top-of-rack: 96 access ports in two rack units is roughly double the density of a 48-port 1RU leaf per U, which is what makes it economic to concentrate several racks of servers onto one switch pair instead of buying a leaf per rack.

Where a 96-port 25GbE switch belongs in a leaf-spine fabric

In a two-tier leaf-spine design, leaves terminate servers and spines terminate leaves. Every leaf connects to every spine, so east-west traffic between any two servers is always two hops, and you scale bandwidth by adding spines rather than by widening a core.

The S5296F-ON is a leaf built for consolidation. Its 96 access ports at 25GbE deliver 2.4 Tbps of access bandwidth against 800 Gbps of uplink across the eight 100GbE QSFP28 ports - a 3:1 oversubscription ratio. For general-purpose virtualization and web tiers, 3:1 is a normal and well-tested design point. For storage-heavy or RDMA workloads you would either move to a 1.5:1 model such as the S5248F-ON, or accept 3:1 and place the latency-sensitive nodes on the same switch so their traffic never leaves the box.

Two S5296F-ON units in a Virtual Link Trunking pair give you 192 active 25GbE server ports with no spanning-tree blocked links, at four rack units total. That density is the entire reason this model exists, and it is why it is the most cost-effective way to light up a large 25GbE access layer on the secondary market.

Density economics: what 96 ports of 25GbE actually buys

A 25GbE SFP28 port and a 10GbE SFP+ port are the same cage, the same single electrical lane and the same one-cable-per-server cabling. Only the lane rate differs, so moving an access layer from 10GbE to 25GbE multiplies usable bandwidth by 2.5x without adding a port, a fibre run or a rack unit.

Density compounds that. At 96 access ports in 2RU, the S5296F-ON delivers roughly double the 25GbE ports per rack unit of a 48-port 1RU leaf, so the same access layer costs you half the rack space, half the uplink count and half the number of switches to manage and patch. Against a 10GbE 1RU leaf the combined effect is a factor of five in access bandwidth per rack unit.

What you trade for it is failure-domain size and uplink ratio. Ninety-six servers behind one chassis is a bigger blast radius than forty-eight, and the eight 100GbE uplinks give 3:1 oversubscription rather than the 1.5:1 a S5248F-ON achieves. Both are managed the same way: deploy in Virtual Link Trunking pairs, and keep latency-sensitive or storage-heavy nodes on a lower-ratio switch.

Breakout: turning 8 uplinks into 32 access ports

Each 100GbE QSFP28 port is four 25GbE lanes in one cage, so a breakout cable turns one QSFP28 port into four 25GbE or four 10GbE ports. Across all eight uplink ports that is 32 additional 25GbE or 10GbE ports, giving a maximum of 128 ports of 25GbE or 128 of 10GbE on a single S5296F-ON if you spend every uplink on access.

The uplinks are also multi-rate: 8 ports of 40GbE natively, or 16 ports of 50GbE via breakout. In practice most designs split the difference - four uplink ports left at 100GbE for the spine, four broken out to 16 extra 25GbE access ports for a few dense nodes.

Airflow: standard and reverse builds

This listing covers both airflow builds of the S5296F-ON. Select the direction under the Airflow option: air direction is set by the power supplies and fan modules physically fitted, so it is chosen when the unit is built rather than switched afterwards. Power supplies and fans must both face the same way - a mismatched pair raises the switch's incompatible-airflow alarm.

Standard airflow (I/O to PSU)

This unit is built for I/O Panel to PSU airflow - Dell's standard direction. Cool air enters at the port face and exhausts at the power-supply and fan face. That is the right choice when the switch is racked with its ports facing the cold aisle.

If your switch will sit with its port face toward the hot aisle - a very common cabling choice, because it puts the switch ports on the same side as the server NICs - you want the reverse-airflow build instead, so the switch is not inhaling its own row's exhaust. Power supplies and fan modules are direction-specific and are not interchangeable between the two builds, so this is a decision to get right at order time rather than in the rack.

Reverse airflow (PSU to I/O)

A 96-port switch is rarely a top-of-rack switch. At that density it usually sits in a dedicated network cabinet in the middle or at the end of a row, aggregating servers from several racks over structured copper or fibre back to one pair of switches. That changes the airflow question, which is why the reverse-airflow build is the one most middle-of-row designs end up ordering.

The reason is cable management. In a middle-of-row cabinet, patch panels and the switch port face are almost always oriented toward the hot aisle, because that is the side the horizontal cabling arrives on and the side technicians work from. A switch whose port face points at the hot aisle must pull its intake air from the power-supply face - the cold side - and exhaust out through the ports. That is exactly what this build does. Install a standard-airflow switch in the same position and it will inhale the row's exhaust from the first day, run hot, and spin its fans harder for the rest of its service life.

The second consideration at this density is thermal load. The S5296F-ON draws up to 893W and dissipates up to 3,047 BTU/h at full load, roughly 1.4x a fully loaded 48-port 1RU leaf. In a shared network cabinet with patch panels and no server airflow to help, that is worth checking against the cabinet's per-rack cooling budget before you commit to consolidating several racks onto one pair of switches.

Two of these in a Virtual Link Trunking pair - four rack units, 192 active 25GbE server ports, no spanning-tree blocked links - is the densest 25GbE access layer you can assemble from the S5200-ON generation.

The reverse-airflow build of the S5296F-ON. Dell calls the two directions by where the air goes: I/O Panel to PSU airflow is the standard build, drawing cool air in at the port face and exhausting it at the power-supply and fan face. PSU to I/O Panel airflow is the reverse, drawing air in at the power-supply face and exhausting it out of the port face. Our -RA SKU is the PSU-to-I/O-Panel unit.

Which one you need is decided by which way the switch faces in the rack, not by preference. In a hot-aisle/cold-aisle row, servers pull cool air from the cold aisle at the front and exhaust into the hot aisle at the back. If you rack a top-of-rack switch with its port face toward the cold aisle, standard airflow is correct. If you rack it with its port face toward the hot aisle - which is extremely common, because it puts the switch ports on the same side as the server NICs and halves your cable runs - then a standard-airflow switch would be inhaling your own hot exhaust. That is the case the reverse-airflow build exists for.

Two practical consequences. First, power supplies and fan modules are direction-specific: Dell ships different part numbers for each direction, and a fan module pulled from a standard-airflow unit will not convert a chassis. Second, mixing directions inside one row is the most common cause of a "this switch runs hot" complaint that has nothing to do with the switch - it is simply pushing hot exhaust into a cold aisle.

Fabric features you get regardless of port count

Every S5200-ON shares the same feature set, so the choice between models is a question of port density rather than capability. All of them carry a 32 MB packet buffer and support Virtual Link Trunking and Routed VLT for multi-chassis active-active pairs without a spanning-tree blocked link. All of them do VXLAN gateway bridging and routing at line rate, and under SmartFabric OS10 they add BGP EVPN with Integrated Routing and Bridging in both asymmetric and symmetric modes, which is what lets you build a controller-less network virtualization overlay.

For converged storage traffic the family implements the full Data Center Bridging set: priority flow control (802.1Qbb), enhanced transmission selection (802.1Qaz), DCBx and iSCSI TLV, plus Routable RoCE so RDMA traffic can cross a leaf-spine boundary. OS10 also supports Precision Time Protocol (IEEE 1588v2) in hardware. Layer 3 is a full stack - OSPF, BGP, policy-based routing, IPv4 and IPv6 - not a licence-gated subset.

SmartFabric OS10, SONiC and what a licence actually means on the used market

The S5200-ON is an ONIE switch, and that is the single most important thing to understand before buying one second-hand. Dell decouples the hardware from the network operating system: the spec sheet's own ordering table lists every model in both a Dell SmartFabric OS10 build and a NO-OS build, on identical hardware. The Open Network Install Environment on the switch will install SmartFabric OS10, Enterprise SONiC Distribution by Dell Technologies, or a third-party network operating system, and the chassis does not care which one you choose.

What you are buying from us is the hardware. A Dell OS10 entitlement is a licence bound to the unit's service tag and to a Dell account, and it does not automatically travel with a switch on the secondary market. A refurbished unit may well arrive with OS10 already installed and fully functional, and it may not carry an active entitlement or a Dell support contract. We do not promise a transferred Dell licence, a software subscription or a support contract with a refurbished switch, and you should be suspicious of any reseller who does.

The practical approach is to plan the NOS as a separate line item: budget an OS10 or Enterprise SONiC subscription from Dell if you need vendor support and TAC escalation, or run community SONiC or another ONIE-compatible NOS if you are comfortable owning the software stack yourself. Tell us what you intend to run and we will tell you what state a specific unit is in before it ships.

Common questions

Is this the standard-airflow or the reverse-airflow build?

Standard - I/O Panel to PSU. Air enters at the port face and exhausts at the power-supply face. The reverse-airflow build is a separate product: Dell PowerSwitch S5296F-ON Reverse Airflow.

Why 2RU when the rest of the family is 1RU?

96 SFP28 cages plus eight QSFP28 cages do not physically fit across a single 1RU faceplate. The second rack unit buys roughly double the 25GbE port density per U compared with a 48-port 1RU leaf, which is the entire point of the model.

What uplink ratio should I plan for?

3:1 as built - 2.4 Tbps of 25GbE access against 800 Gbps of 100GbE uplink. If that is too thin for your east-west traffic, the S5248F-ON runs 1.5:1 at half the port count.

Choosing within the S5200-ON family

All five models share the same operating system, the same 32 MB buffer and the same Layer 2 and Layer 3 feature set. You are choosing density and uplink ratio, nothing else.

Stepping up a generation, the Dell PowerSwitch S5448F-ON moves the same design language to 100GbE access and 400GbE uplinks.

Condition, testing and what ships in the box

This is a refurbished, professionally reconditioned unit. Every switch is powered up, inspected and functionally tested before it leaves us, and it ships with warranty coverage. Power supplies, fan modules, rail kits, console cables and optics are configurable above - choose the airflow direction that matches the chassis, because power supplies and fans are direction-specific parts.

If you need a specific firmware or NOS state, a specific optics loadout, or matched pairs for a VLT domain, tell us before you order and we will build to it.

Specifications