Dell Networking Z9100-ON 100GbE Switch

The Dell Networking Z9100-ON is a 1RU fixed-configuration data centre switch with 32 QSFP ports that accept either QSFP28 100GbE or QSFP+ 40GbE modules, two hot-swappable power supplies with integrated fans, separate hot-swappable fan modules, and a choice of two airflow directions.

It was Dell's first-wave open networking spine: 32 cages of 100GbE in a single rack unit, sold as bare hardware with ONIE rather than a locked operating system. That combination is exactly why it is still bought second-hand a decade later - the port density is still relevant for aggregation, and the software is still yours to choose.

What a 32x100GbE spine is actually for

A leaf-spine fabric is built from two shapes of switch. The leaf terminates servers and storage at 10 or 25GbE; the spine terminates the leaves at 40 or 100GbE and does nothing else. The Z9100-ON is a spine. Every one of its 32 ports is the same speed and the same cage type, which is what you want in a spine - the design is deliberately boring so that every leaf sees an identical path.

Thirty-two ports of 100GbE gives you a fabric that can carry thirty-two leaf switches at full 100GbE uplink, or sixteen leaves at 2x100GbE for link redundancy, in one rack unit and one power budget. For an enterprise or mid-size cloud that is a whole data hall's worth of spine. For a lab or a burn-in rack it is a 100GbE core that draws 288W typical.

The multi-rate part matters just as much as the port count. Each of the 32 cages takes a QSFP+ module as readily as a QSFP28, so the same chassis can front a 40GbE estate today and a 100GbE estate after a module swap. Buying a spine that can serve both speeds is the whole argument for a multi-rate switch over a single-speed one.

ONIE, and why bare hardware is a feature on the used market

The "-ON" suffix is Dell's open networking designation and it is the single most important thing to understand before buying one of these second-hand. The switch ships with the Open Network Install Environment - a small bootloader whose only job is to fetch and install a network operating system over the network. It is not an operating system itself.

That decoupling is why a used Z9100-ON is not the licensing trap that a used vendor-locked switch can be. The hardware you buy is the hardware; the software you run is a separate decision made at install time. Dell Networking OS is the native choice, and the ONIE bootloader will equally install an alternative ONIE-compatible network operating system. If your fabric is already standardised on something else, the switch will take it.

The practical consequence for a buyer: check what is installed on arrival, and expect to reinstall. A switch that arrives at the ONIE prompt is not broken - it is in the state Dell intended.

Airflow direction: get this right before it is racked

The Z9100-ON supports two airflow directions, and only one of them per chassis. Normal airflow runs from the I/O panel to the power supplies; reversed airflow runs from the power supplies to the I/O panel. Dell is explicit that the two must never be mixed - both power supplies and every fan module have to face the same way.

Which one you want is decided by how the switch sits in the rack. If the port face is in the cold aisle, normal airflow is correct. If the port face is in the hot aisle - which is the common choice, because it puts the switch ports on the same side as the server NICs - you want reversed airflow so the switch is not inhaling its own row's exhaust.

Changing direction after the fact is possible but not casual: it requires the unit powered down and every fan module and power supply unit replaced with matching-direction parts. It is a decision to make at order time. If you are unsure which direction your rack layout needs, ask before you order - the airflow build is configured on this page.

Power, cooling and the redundancy rules

Two hot-swappable power supplies sit in the utility panel, and both bays must be populated. Dell states plainly that the switch must not be run on a single PSU. The supplies carry their own integrated fans, and there are separate hot-swappable fan modules as well; every fan slot must contain a working unit or the system shuts itself down within one minute. Hot-swapping a fan or a fan-power supply is only safe when the second, redundant supply is installed - which is another way of saying the 1+1 configuration is not optional.

Both AC and DC supplies exist, and they must not be mixed in one chassis. AC draws 100-240 VAC at 50/60 Hz with a 606W maximum and a 288W typical consumption. The DC variant runs from -48 V or -60 V at up to 32 A. There is no on/off switch: connect a cord and the switch powers up.

Thermally the switch is rated to 113 F (45 C) ambient, with a 1 C derate per 300 m above 950 m of altitude, and it puts 1153 BTU/hr into the room at full tilt. Leave five inches of clearance front and back.

Where it sits against the rest of the Dell 100GbE line

Within Dell's own range the Z9100-ON is the entry point to 100GbE spine, and the family scales up from it rather than around it. The Z9264F-ON doubles the density to 64 ports of 100GbE in 2RU and is the natural upgrade when 32 spine ports stop being enough. The S6100-ON reaches a similar 32-port 100GbE count but does it modularly, across four I/O module bays, which suits an estate that is mid-migration between 40 and 100GbE. Above all of them, Z9432F-ON and Z9664F-ON move the fabric to 400GbE.

For anyone buying refurbished, the Z9100-ON's argument is cost per 100GbE port. It is the oldest switch in that list, which is exactly why it is the cheapest route into a real 100GbE fabric, and its QSFP28 cages take the same commodity 100GbE DACs and breakout cables the rest of the industry uses.

Cabling and optics

Each of the 32 cages is a standard QSFP28, so the switch cables with ordinary passive 100GBASE-CR4 direct-attach twinax at 0.5 to 5 metres for in-rack and adjacent-rack runs, and with 100G-to-4x25G breakout DACs where a spine port needs to feed four 25GbE endpoints. Optical QSFP28 modules fit the same cages for longer runs. Dell's own guidance is to consult the supported-optics list before ordering modules; if you tell us the reach and the far-end device we will confirm compatibility before the unit ships.

Every unit is professionally reconditioned, fully tested and shipped with warranty. Rack mounting uses the Dell ReadyRails system for tool-less 1U front-rack and two-post installation, and the chassis will equally sit on a shelf or mount directly into a 19 inch EIA-310-E rack.

Specifications