Dell Networking S4148FE-ON 10GbE Switch

The Dell Networking S4148FE-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 member of the S4100 family that supports 10GBASE-LRM optics. That single capability lets it run 10 Gigabit Ethernet over the OM1 and OM2 multimode fibre already installed in older buildings.

Where the S4148FE-ON sits in a data center

Most 10GbE optics assume OM3 or OM4 fibre. A building wired in the 1990s or early 2000s is usually OM1 or OM2, and on that fibre a standard 10GBASE-SR link will not reach a useful distance because modal dispersion closes the eye long before the power budget runs out. 10GBASE-LRM was written for exactly this case: it uses electronic dispersion compensation in the receiver to hold a 10GbE link over legacy multimode.

So the S4148FE-ON is the answer to a specific question - "we need 10GbE in this building and we are not re-pulling the fibre." Everywhere else in the family the F model is the better buy. Here, the alternative is a cabling project, and the switch is cheaper than the trenching.

Beyond that, it behaves as a conventional high-density ToR switch: 48 server-facing 10GbE ports with 100GbE uplinks into a spine, VLT for multi-chassis redundancy, and full L3.

Port layout and breakout math

The port face is 48x SFP+ plus two QSFP+ and four QSFP28 cages, identical to the S4148F-ON. The QSFP28 ports are multi-rate: 100GbE, 40GbE, 4x 25GbE, 4x 10GbE or 2x 50GbE per cage. Breaking out all four QSFP28 ports to 4x 10GbE alongside the 48 fixed ports gives the sheet's maximum of 72x 10GbE in 1U. Maximum densities are 72x 10GbE, 16x 25GbE, 6x 40GbE, 8x 50GbE and 4x 100GbE, each figure assuming the rest of the cages are used accordingly.

Port-to-port latency is 850 nanoseconds. That is marginally higher than the 800 ns of the S4148F-ON and is the price of the LRM-capable receive path; for storage and general server traffic the difference is immaterial, and only latency-sensitive HPC workloads would notice.

The LRM difference, stated precisely

The S4100 spec sheet makes two separate statements about this. In the performance section it says LRM optics are supported "on S4148FE-ON product (not supported on other products in S4100 product family)". In the supported-optics list, the LRM transceiver line carries the qualifier "(for S4148FE only)". Both refer to the same capability.

Two practical consequences. First, the optic matters as much as the switch - an SR transceiver in an S4148FE-ON is still an SR link and will not rescue OM1 fibre. Second, if you are replacing an S4148F-ON with an FE to gain LRM, you also need LRM transceivers at both ends of each link, which means the far-end device has to support them too.

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.

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.

Operating system and licensing on a used S4148FE-ON

ONIE is pre-installed, and the switch runs Dell EMC Networking OS10 Enterprise Edition. Because it is an open-networking platform, the same hardware will accept a third-party network operating system - though LRM support is a function of the optic and the PHY rather than the NOS, so it survives a re-image.

Layer 3 covers OSPF, BGP, policy-based routing and VRF-lite. VLT provides multi-chassis link aggregation; there is no stacking on this family, which is the correct design for a ToR pair because each chassis keeps an independent control plane.

Choosing between the S4000-series models

• S4148F-ON - the same port layout without LRM, 800 ns latency, 370W maximum draw. The default choice unless you specifically need LRM.
• S4148U-ON - adds unified ports for 8/16/32G Fibre Channel on the same chassis.
• S4148T-ON - 48x 10GBASE-T copper instead of SFP+.
• S4128F-ON - 28 ports with 2x 100GbE uplinks.
• S4112F-ON - 12 ports, half-rack width, for edge cabinets.

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