Dell Networking S4148U-ON Unified Switch

The Dell Networking S4148U-ON is a 1U top-of-rack switch with 48 ports of 10GbE SFP+, two 40GbE QSFP+ ports and four 100GbE QSFP28 ports, and it is the only model in the S4100 family whose ports can be reconfigured as Fibre Channel. Twenty-four of the SFP+ ports and all four QSFP28 ports are unified, so the same chassis can carry Ethernet and FC traffic at the same time.

Where the S4148U-ON sits in a data center

This is a convergence switch. In a rack that runs both IP traffic and a Fibre Channel storage fabric, the usual arrangement is two separate switching layers: an Ethernet ToR pair and an FC pair, each with its own cabling, optics, spares and management. The S4148U-ON collapses that into one pair of 1U boxes. Up to 40 ports can be presented as 8G or 16G FC in an oversubscribed profile, 28 at 16G line rate, 16 at 32G oversubscribed, or 8 at 32G line rate - with the remaining ports still serving 10GbE server access.

That makes it a natural fit in front of an FC-attached array where the compute side has already moved to 10GbE, and in mixed estates that are part-way through a migration from FC to iSCSI or NVMe/TCP and need both fabrics live at once. The four 100GbE QSFP28 uplinks give the switch a spine connection that will outlast the storage transition.

Port layout and breakout math

The port face is 48x SFP+ plus two QSFP+ and four QSFP28 cages. The QSFP28 ports are multi-rate: each will run at 100GbE, or 40GbE, or break out to four 25GbE or four 10GbE lanes, or two 50GbE. Taking all four to 4x10GbE and adding the 48 fixed SFP+ ports yields the sheet figure of 72 ports of 10GbE from one rack unit. The 40GbE QSFP+ ports also step down to 10GbE. Maximum densities are 72x 10GbE, 16x 25GbE, 6x 40GbE, 8x 50GbE and 4x 100GbE - not simultaneously, since breakout consumes the parent cage.

Unified ports are a software profile, not a hardware variant: the switch is reconfigured between Ethernet and FC roles in OS10 rather than by fitting a different card. What does change is the transceiver. FC ports need FC optics, and the S4100 sheet lists four of them explicitly marked "(S4148U model only)". Budget for those separately - an Ethernet SR optic will not negotiate a Fibre Channel link.

Airflow: standard and reverse builds

This listing covers both airflow builds. Select the direction under the Power Supply & Airflow option: 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)

The normal-airflow (NA) build, also written I/O-to-PSU or front-to-back. Air enters at the port face and exhausts at the power-supply end. Fit it when the switch is mounted with its ports facing the hot aisle, the conventional orientation in a cold-aisle-containment room where servers also pull from the front.

Reverse airflow (PSU to I/O)

The reverse-airflow (RA) build, sometimes written PSU-to-I/O or back-to-front. Air is drawn in at the power-supply end and exhausted out of the port face. Fit it when the switch presents its ports to the cold aisle - the common arrangement when you want to patch from the front of the rack and keep cabling out of the hot aisle.

Operating system and licensing on a used S4148U-ON

The S4148U-ON ships as an open-networking platform with ONIE pre-installed, and runs Dell EMC Networking OS10 Enterprise Edition. Unified-port reconfiguration is an OS10 feature, so the FC capability depends on the installed image rather than on the hardware alone - a point worth confirming before you plan a converged deployment on a second-hand unit. ONIE also means the switch can be re-imaged with a third-party network operating system, though FC support is a Dell OS10 capability and does not travel to other NOS images.

Layer 3 is full-featured: OSPF, BGP, policy-based routing, VRF-lite and VLT for multi-chassis redundancy. There is no stacking - VLT is the mechanism for pairing two units into one logical uplink target, and it is the better choice in a ToR role because each half keeps its own control plane.

Choosing between the S4000-series models

Within the S4100 family the chassis, fabric and management are common; the differences are on the port face:

• S4148F-ON - the same 48x SFP+ / 2x QSFP+ / 4x QSFP28 layout, Ethernet only. Pick it if you have no FC requirement; it draws less power (370W maximum against 460W) and costs less to run.
• S4148FE-ON - identical port count, and the only model that supports 10GBASE-LRM optics over legacy OM1/OM2 fibre.
• S4148T-ON - the copper twin: 48x 10GBASE-T instead of SFP+, for short in-rack runs on RJ45.
• S4128F-ON - 28 ports and 2x 100GbE, for a half-populated rack.
• S4112F-ON - the 12-port half-rack-width model for edge and small-cabinet deployments.

The S4148U-ON only makes sense if you actually need Fibre Channel. If you do not, the S4148F-ON is the same switch without the unified-port licence overhead and the higher power draw.

Condition, testing and warranty

Refurbished units are cleaned, inspected and functionally tested before they ship: every port is link-tested, both power supplies and all four fan modules are verified, and the unit is booted and checked for fault codes. Configuration is cleared. Units ship with warranty; the coverage tier is selected on this page.

Specifications