Dell PowerSwitch S5448F-ON 100GbE Switch

The Dell PowerSwitch S5448F-ON is a 1RU multi-rate aggregation switch with 48 ports of 100GbE SFP56-DD, 8 ports of 400GbE QSFP56-DD and two 10GbE SFP+ ports, driven by a 16 Tbps full-duplex non-blocking fabric, 2.6 Bpps of forwarding capacity and an 82 MB packet buffer.

It is the newest heavy iron in Dell's fixed-format switch line to reach the secondary market, and it is a genuine generational step rather than a port-count refresh: the buffer is roughly 2.5x that of the S5200-ON generation, the fabric is five times the capacity of a 32x100GbE spine, and it puts 400GbE uplinks in one rack unit.

Where a 100/400GbE switch belongs

The S5448F-ON sits one tier above the 25GbE access layer. Its 48 SFP56-DD ports terminate 100GbE - which in practice means leaf uplinks, storage arrays, GPU nodes and high-throughput compute - and its eight QSFP56-DD ports carry 400GbE up to a spine or across a data-hall boundary. That works out to 4.8 Tbps of 100GbE access against 3.2 Tbps of 400GbE uplink, a 1.5:1 ratio in a single rack unit.

Used as a spine, it terminates 100GbE uplinks from 48 leaves at line rate. Used as an aggregation switch, it collapses what used to be a multi-unit 100GbE core into 1RU. The 82 MB packet buffer is the specification that matters most in both roles: aggregation points are where incast happens, and buffer is what absorbs it. At 82 MB it carries roughly 2.5x the buffer of the S5200-ON generation's 32 MB.

One qualification, stated plainly because Dell states it: the fabric is described as non-blocking for packets larger than 364 bytes. For anything resembling normal data centre traffic that is a non-issue; for synthetic small-packet benchmarking it is worth knowing before you test.

SFP56-DD, PAM4, and the optics warning that comes first

Read this before you order optics. The 48 100GbE SFP56-DD ports on the S5448F-ON use PAM4 signalling - two 50G serdes lanes - and not the NRZ signalling (four 25G lanes) that QSFP28 100GbE uses. Dell states it explicitly in the spec sheet: QSFP28 optics and break-out will not work on the SFP56-DD ports. If you are moving up from an S5232F-ON, a Z9100-ON or any other QSFP28-based 100GbE switch, your existing 100GbE optics and DACs do not carry over to the SFP56-DD ports. Budget for SFP56-DD optics.

The eight QSFP56-DD ports are the flexible ones. They are multi-rate across 10/25/40/50/100/200/400GbE, so a 400GbE cage can be run as a single 400GbE link, broken out to lower rates, or populated with a 100GbE-class module when you need the reach rather than the bandwidth. The SFP56-DD ports are multi-rate across 10/25/50/100GbE.

Optics power budgets are worth checking against your intended modules, because they are tighter than most switches: up to 5W per module in all 48 SFP56-DD ports, and up to 15W in all eight QSFP56-DD ports with four of them scaling to 18W. Those figures drop in the reverse-airflow direction - see the airflow section below.

Airflow: standard and reverse builds

This listing covers both airflow builds of the S5448F-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)

The reverse-airflow build of the S5448F-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. Third, and specific to this model: Dell footnotes that units built in the PSU-to-I/O-Panel direction are subject to tighter optics power limits on the 100 and 400GbE ports. Concretely, the 48 SFP56-DD ports support up to 5W per module in the standard direction but 3.5W across all 48 in the reverse direction, with 24 of them scaling to 5W; the eight QSFP56-DD ports support up to 15W (4 scaling to 18W) in the standard direction but 6W across all 8 in the reverse direction, with 4 scaling to 10W. If you are planning high-power 400GbE coherent or long-reach modules, check them against those reverse-direction budgets before you order.

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

Can I reuse my existing 100GbE QSFP28 optics?

No. The 48 100GbE ports are SFP56-DD and use PAM4 signalling on two 50G lanes. Dell states directly that QSFP28 optics and QSFP28 breakout will not work in them. This is the single most expensive mistake to make with this switch, so plan SFP56-DD optics from the start.

Is it really non-blocking?

Dell qualifies it: non-blocking for packets larger than 364 bytes. For production traffic that is a non-issue; for small-packet synthetic benchmarking it is worth knowing up front.

How does the buffer compare with the S5200-ON generation?

82 MB against 32 MB - roughly 2.5x. At an aggregation point, where incast happens, buffer is the specification that decides whether microbursts turn into drops.

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

Standard - I/O Panel to PSU. The reverse-airflow build is a separate product and carries tighter optics power budgets: Dell PowerSwitch S5448F-ON Reverse Airflow.

Where it sits against the S5200-ON generation

The S5200-ON family is the 25GbE access generation: S5212F-ON and S5224F-ON for low-density racks, S5248F-ON as the mainstream 48-port leaf, S5296F-ON for 96-port middle-of-row consolidation and S5232F-ON as the 32x100GbE spine. The S5448F-ON is the tier above all of them - it terminates their 100GbE uplinks and carries 400GbE onward. Note that its optics are not interchangeable with theirs: they are QSFP28/NRZ, the S5448F-ON's 100GbE ports are SFP56-DD/PAM4.

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