UniFi Switch 24

Ubiquiti · rack-mount switch, 1U · US-24

what it is

A managed switch for a 19-inch rack, 1U high: twenty-four gigabit ports and two SFP fiber transceiver slots. Steel enclosure of 443 × 221 × 43.7 mm, consumption up to 24 W. It has a fan.

This model has no PoE, and that is the first thing to check before ordering. The identical-looking US-24-250W does have PoE, but it is also noticeably larger — 485 mm instead of 443 and 285 mm deep instead of 221. Access points and cameras require that model or separate power.

what we read from it

The status of each of the twenty-six ports separately — whether the link is up, at what speed, in what duplex, how many errored frames passed and how many times the link went down since the last boot.

Things that in practice resolve support tickets:

• Link-down counter per port. A cable that drops once a day looks the same as a healthy one at the moment you look at it. The counter shows the difference.
• Spanning tree (STP) changes, i.e. the mechanism that makes sure there are no loops in the network. A rising counter on a single port usually means a loop or a device that keeps switching between two paths.
• Which device sits in which port — together with its hardware address. You can see what is connected behind what without walking to the rack with a flashlight.
• Uptime since power-on. A switch that "works" but came up fifteen minutes ago points to a power interruption nobody reported.
• Internal temperature — the general_temperature field in the list below.

port layout

The twenty-four copper ports are arranged in two rows of twelve, in two blocks of six columns. Numbering runs down, then right: 1, 3, 5… on top and 2, 4, 6… on the bottom. Adjacent numbers are therefore not side by side but one above the other — when looking for a cable in the rack, this is the first thing that confuses people.

The two SFP slots are stacked at the right edge: the upper one is port 25, the lower one 26. They are one-gigabit slots, not 10G — this matters when planning a link between racks.

On the left side of the panel, a large square system LED with the manufacturer's logo lights up. On the back face there is a power inlet, a fan grille and a separate serial console port, which the manufacturer does not count among the twenty-six.

what to watch out for

• The fan level from the controller does not tell you whether the fan is spinning. The controller reports level 0 for the entire first generation of UniFi switches regardless of temperature.
• Temperature is compared within the model. The sensor measures the interior, while the manufacturer specifies an ambient temperature limit. In one sample from October 2026, units of this model read 42–53°C, and one in a closed shaft read 64°C.
• There is no cable test. UniFi Network controller 10.6.106 has no such function at all.
• SNMP responds, but the switch silently truncates an access password (community) longer than 20 characters. It then responds only to the first 20 characters and stays silent for the full one — which looks like SNMP being disabled.

what we cannot read

• PoE — this model does not have it. That is a hardware limit.
• Fan speed — there is internal temperature, not RPM.
• Traffic broken down by individual device over time. The counters are cumulative, and the history for each client has to be built separately.

transceivers tested in this device

Transceivers we checked in this device, and whether the device showed their optical diagnostics (temperature, power, alarm thresholds):

• Unbranded GLC-LH-SM (1000BASE-LX/LH), firmware 7.4.1.16850: diagnostics read (1 units).
• Ubiquiti UF-MM-1G (1000BASE-SX), firmware 7.5.15.17146: diagnostics read (1 units).
• E2O Communications ES212-LP3TA-A-F1 (1000BASE-LX; Fibre Channel 1/2G LW), firmware 7.5.15.17146: diagnostics not shown (4 units).
• Unbranded GLC-LH-SM (1000BASE-LX/LH), firmware 7.5.15.17146: diagnostics not shown (1 units).
• TP-Link TL-SM311LM (1000BASE-SX), firmware 7.4.1.16850: diagnostics not shown (1 units).

All transceivers and switches in one place, with filters: what each device shows.

full parameter list from the controller interface

The list shows WHAT the device exposes — including parameters we do not use ourselves. There are no values here at all: it is a catalog of capabilities, not a reading from anyone's network. It is not a closed list either — explanation below the table.

570 parameters

List source: reading of 7 working units (as of 2026-09-27). The list is the sum of what we observed — more units reveal more parameters, so numbers for different models are not directly comparable.

full list of parameters read via SNMP

This list comes from a different reading path than the controller list above. These are objects the device itself returns over SNMP (names from MIB files). There are no values here, and no port numbers either.

104 parameters

SNMP list source: reading of 3 units (as of 2026-10-18); sample counted separately from the controller list.