What is a Small Form-factor Pluggable?

A Small Form-factor Pluggable (SFP) is a compact, hot-swappable transceiver module that inserts into an Ethernet port cage on a Versa CSG or CSX appliance, converting the switch’s internal signaling to fiber or copper cabling. Speed-scaled variants – SFP, SFP+, SFP28, and QSFP28 – cover 1-Gigabit through 100-Gigabit Ethernet links.

Key takeaways

• SFP is a compact, hot-swappable transceiver for switch and gateway ports.
• Speed variants scale from SFP (1G) through SFP+, SFP28, to QSFP28 (100G).
• CSX and CSG appliances validate specific SFP models per port group.
• Fiber, copper, AOC, and DAC options match cabling to distance and cost.
• Only Versa-validated transceivers are supported on production ports.

On this page: Why it matters · How it works · SFP transceiver types · SFP transceivers & Versa hardware · FAQ

Why are Small Form-factor Pluggables important?

Switch and gateway silicon is fixed once an appliance ships, but site cabling rarely is: one run is short copper, the next is single-mode fiber, at speeds from 1-Gigabit access to 100-Gigabit uplinks. The SFP cage solves that mismatch by putting the media-dependent part of the port – optics or copper PHY – in a removable module rather than soldering one choice onto the board. The same CSX chassis serves a copper-only closet and a fiber-fed aggregation rack; only the transceiver changes.

Hot-swap capability matters too: a failed optic or a move from 10-Gigabit to 25-Gigabit fiber is a module swap, not a device replacement. Versa validates exact supported part numbers per port group, so operators know a given SFP will link reliably before ordering it.

What is a Small Form-factor Pluggable?

Physically, an SFP is a small metal-and-plastic module with an edge connector on one end and a duplex LC fiber or RJ-45 copper jack on the other, held in the port cage by spring contacts and a release latch. Internally it carries the transceiver electronics and an ID chip the switch reads to identify its type. Transceivers from multiple manufacturers – Finisar, Edgecore, and FS appear throughout Versa’s validated lists – are interchangeable as long as they match the port’s supported type.

The family scales by physical size and lane count: SFP and SFP+ share one cage across 1-Gigabit and 10-Gigabit Ethernet; SFP28 reuses it for 25-Gigabit; QSFP28 is a wider four-lane module for 100-Gigabit, fanning out into four lower-speed links. Which port groups accept which family depends on the Broadcom controller wired to that group.

SFP transceiver types

Versa’s validated lists group transceivers by reach and media. Short reach (SR/SX) modules use multimode fiber for runs up to a few hundred meters – the common in-rack choice. Long reach (LR/LX) modules use single-mode fiber and reach up to 10 kilometers, for building-to-building or campus-core links. Copper optics (1000BASE-T or 10GBASE-T RJ-45) let an SFP-only port run over existing copper cabling. Dual-rate transceivers auto-negotiate between two speeds – 1-Gigabit/10-Gigabit or 10-Gigabit/25-Gigabit – on one port group.

Two cable assemblies replace a transceiver-plus-patch-cable pair for short runs: direct-attach copper (DAC), a passive twinax cable with a transceiver molded onto each end, and active optical cable (AOC), the fiber equivalent. Breakout cables extend both, fanning a QSFP28 head end out to four SFP+ or SFP28 tail ends.

SFP transceivers & Versa hardware

Versa publishes a validated SFP and cable list per appliance series, because port groups on the same chassis are wired to different Broadcom controllers. On the CSX4000 series, ports enet-0/0 through enet-0/47 run 1-Gigabit copper, enet-0/48 through enet-0/51 run 10/25-Gigabit fiber, and the two 100-Gigabit QSFP28 ports are enet-0/52 and enet-0/56 – each group on its own controller. CSX8000 series appliances follow the same pattern at higher port counts.

Configuration follows the hardware: a breakout port is enabled with a CLI command such as set interfaces enet-0/52 breakout-mode 4x10g, and LED color reports the negotiated media speed. The CSX4000 hardware guide documents the port layout, and the validated-transceiver guides for CSX4000 and CSX8000 list the exact supported part numbers per port group.

Frequently asked questions

Can I use any SFP transceiver in a Versa appliance port?

No. Each port group is wired to a specific controller with its own supported transceiver list, published per appliance series. An unlisted optic may fail to link or fall outside Versa TAC support – check the validated SFP guide for the appliance before ordering.

What is the difference between SFP, SFP+, SFP28, and QSFP28?

They are speed classes on related form factors: SFP tops out at 1-Gigabit, SFP+ at 10-Gigabit, and SFP28 at 25-Gigabit, all sharing one cage size. QSFP28 is a wider four-lane module for 100-Gigabit, which can break out into four lower-speed links.

Do I need to power down an appliance to swap an SFP?

No. SFPs are hot-swappable by design: a module can be inserted or removed while the appliance is powered on and passing traffic on its other ports. Only the affected port’s link drops briefly; the rest of the chassis is unaffected.

What is the difference between a DAC cable and a transceiver-plus-fiber setup?

A direct-attach copper (DAC) cable integrates two transceiver ends and a fixed-length cable into one assembly, suited to short in-rack runs. A separate transceiver and fiber patch cable costs more per link but supports longer, more flexible runs and mixed-length fiber plants.

Can a 100-Gigabit QSFP28 port be split into smaller links?

Yes. Breakout mode splits a QSFP28 port’s four internal lanes into four independent 10-Gigabit SFP+ or 25-Gigabit SFP28 links, using a breakout cable and a CLI command on the port. Not every port supports breakout – the last port on some models is excluded.

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