Dell PowerSwitch S4820T 10GbE Switch

The Dell Networking S4820T is a 1U top-of-rack switch with 48 ports of 1/10GBASE-T copper and four 40GbE QSFP+ uplinks, delivering 1.28 Tbps of non-blocking, cut-through switching. It is the copper counterpart of the S4810P and the entry point to 10 Gigabit Ethernet on ordinary structured cabling.

Where the S4820T sits today

Be straightforward about the generation. The S4820T predates the S4000 and S4100 families and runs Dell Networking OS9 (FTOS) rather than OS10. There is no 25GbE, no 100GbE and no ONIE support. It is the oldest platform in this catalogue, and it is listed because it still does one job well: 10GbE over copper, cheaply, in a rack that is already cabled with Cat6a.

That job is real. A site with 48 servers on 10GBASE-T LOM ports and an installed base of RJ45 patching has no need of optics, DACs or fibre, and re-cabling to SFP+ would cost more than the switch. The S4820T serves that rack directly. It also works as a lab, staging or out-of-band aggregation switch, and as a like-for-like replacement in an estate that already runs S4820Ts and is not ready to re-platform.

What it is not is a foundation for a new build. If you are designing a fabric today, start with the S4048T-ON or the S4148T-ON.

Port layout and breakout math

Forty-eight 1/10GBASE-T ports handle access over Cat6a, auto-negotiating down to 1GbE and 100Mb for older devices - useful in a mixed rack. Four QSFP+ cages carry the uplinks, each running 40GbE or breaking out to four 10GbE lanes, which is how the platform reaches 64 ports of 10GbE in 1U.

Uplink capacity is the constraint: 160 Gbps of uplink against 480 Gbps of access, with no path to 100GbE on this chassis. If your spine has moved to 100GbE, the S4820T attaches only through a 40GbE-capable spine port.

Like the S4810P, the S4820T stacks - up to six units over user ports, managed as one logical switch. The S4000 generation that replaced it dropped stacking in favour of VLT. Stacking is simpler to run for a small deployment; VLT is more resilient because each chassis keeps an independent control plane.

The copper latency trade, stated honestly

Port-to-port latency is 3.3 microseconds. The fibre S4810P of the same generation is 800 nanoseconds - roughly four times quicker. The difference is not the switching fabric, which is identical at 1.28 Tbps and 960 Mpps; it is the 10GBASE-T physical layer. Encoding a 10 Gigabit signal for twisted pair and decoding it at the far end costs a couple of microseconds, and it is inherent to the standard rather than to this switch.

For virtualisation, file services, backup and general server traffic, three microseconds is invisible. For HPC interconnects, financial messaging or anything that measures latency in microseconds by design, use fibre. The trade is cabling cost against latency, and it is worth making deliberately rather than by accident.

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. On this platform both directions are available with either AC or DC supplies - airflow and power type are independent choices.

Standard airflow (I/O to PSU)

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)

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 management

The S4820T runs Dell Networking OS9 (FTOS), a mature CLI-driven network operating system with a full L3 stack - OSPF v2 and v3, BGP with 4-byte ASN, policy-based routing, VRF-lite for IPv4 and IPv6 - plus VLT for multi-chassis link aggregation and the data-center-bridging set (PFC, ETS, DCBx) for converged storage traffic. Dell's Embedded Open Automation Framework is included, so the switch can be driven from existing configuration-management tooling.

There is no ONIE. This is a closed platform: it runs OS9 and cannot be re-imaged with a third-party network operating system.

Choosing between this and a newer switch

• S4048T-ON - the direct successor. 48x 10GBASE-T with six 40GbE uplinks, 1.44 Tbps, and ONIE for OS10 or a third-party NOS.
• S4148T-ON - two generations on: 48x 10GBASE-T with 2x 40GbE and 4x 100GbE QSFP28 uplinks, 1.76 Tbps. The right choice if the spine is 100GbE.
• S4810P - the fibre contemporary: same 1.28 Tbps fabric and four 40GbE uplinks, but 48x SFP+ and 800 ns latency instead of 3.3 microseconds.
• S4112T-ON - a modern half-rack-width copper switch if you only need twelve ports.

Condition, testing and warranty

Refurbished units are cleaned, inspected and functionally tested before they ship: every port is link-tested, the power supplies and 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