The Ubiquiti Flex Mini 2.5G has been a highly requested review on STH since we launched The Ultimate Cheap Fanless 2.5GbE Switch Buyers Guide. This is a 5-port 2.5GbE switch also known as the USW-Flex-2.5G-5. Low power, PoE-in, and UniFi management make it quite different. At the same time, we opened it up and found that it is the same internal chipset powering some of the 4-port 2.5GbE and 2-port 10G switches that are under $30, which we had not seen anyone go into detail on previously.
As a quick note, we purchased these units thanks to our STH YouTube members. We have refused to sign the “Influencer Testing NDA” with Ubiquiti that everyone else does because there is a line in there that Ubiquiti would not allow us to remove, saying that we could review the product provided Ubiquiti is allowed to review the post prior to publication, and that we would incorporate that feedback if needed. While we tour data centers, manufacturing sites, and similar locations and let people preview to ensure we are not leaking confidential information, we do not allow vendors to preview and provide substantive feedback that we would be required to incorporate into our reviews. Our readers and YouTube viewers have requested that we review this box over the years, so we purchased a few to provide an honest assessment. As a fun one, when Patrick was at Microcenter this week buying extra units, one of the YouTube viewers said hello and commented on the recent Ubiquiti UniFi Cloud Gateway Fiber UCG-Fiber Review.
Patrick’s Editor’s Note: Ubiquiti reached out the evening after this was published and requested edits to be made to the paragraph above. Although disctinctly recall Ubiquiti told me that everyone else signs the “Influencer Testing NDA”, there may be people who did not, so we are going to strike that out. Fair point. We also changed the “standard NDA” to “Influencer Testing NDA” because Ubiquiti, when making the requests, also said that they were not aware of the review and incorporate feedback language in question. While doing that, they had copied the person in Legal who actually e-mailed me the document and who I discussed my concerns with. I have never had a request like this in 16+ years of reviewing products in the industry, especially when we are buying product for editorial review.
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The switch has five 2.5GbE ports as the headline feature. What Ubiquiti is doing is also making the profile of the switch minimally larger than the ports themselves.
Powering the switch can happen over the 5th port, which has PoE IN or a USB Type-C 5V power input. As a quick labeling note, it would have been nice for Ubiquiti to label this as port “5” to match the other four.
The first thing that should strike you about the Flex Mini 2.5G is the size. At only 4.6×3.5×0.8in or 117.1x90x21.2mm it is a very small switch.
In fact, the plastic housing makes it one of the smallest switches in its class. That presents cooling challenges which we will get to when we get inside.
The sides of the switch do not have vents, so there are no obvious vents in the plastic case.
On the top we get the Ubiquiti logo.
Here is the bottom of the unit. There are nice rubber feet installed, but if you were thinking that they are hiding screws to open the case, you would be incorrect. This is another snap together design from Ubiquiti.
You will notice a reset button at the bottom. That pushes on a small reset button at the bottom of the switch PCB.
On the cooling side, Ubiquiti has a challenge. It has a chassis with virtually no airflow, and it is made of plastic, limiting the amount of heat that chips radiate into the environment. Instead of just using a metal chassis and small heatsinks like other devices, Ubiquiti has a custom heat spreader that makes contact with the larger chips and helps cool them. Luckily this is a low-power device.
Here is something really cool. The Realtek RTL8372N is the big switch chip. That is the same switch chip driving many of the 4+2 (4-port 2.5GbE and 2-port 10G) switches on the market because it has two 10G SerDes interfaces.
It appears to be the same as the main switch chip in the Ubiquiti UCG-Fiber as well.
The smaller Realtek chip is the RTL8221B, which is the same as we would find in something like a Yulinca switch going to its 5th 2.5GbE port.
Next, let us get to the performance.