Update Jan 2023: There is an official Ubiquiti product that is MUCH cheaper than the media converter mentioned below, that will now work the way you would expect. It is the UACC-CM-RJ45-MG which is an SFP+ to 10GbE RJ45 Transceiver Module that can negotiate 1GbE/2.5GbE/5GbE/10GbE speeds and this is good for up to 100m on a Cat6a cable. This transceiver can be found at store.ui.com under the Accessories -> SFP Accessories -> 100m variant. This transceiver goes into the SFP WAN port on your UDM-PRO / UDM-PRO SE console. Once plugged in with an RJ45 cable, it will negotiate the 1GbE/2.5GbE or 5GbE ports of your fiber modem. The original transceiver was the UF-RJ45-10G which only negotiated on 1GbE or 10GbE and wouldn't work on the 2.5GbE or 5GbE speeds (I know because I tried). It was discontinued in 2022 in favor of the UACC-CM-RJ45-MG.
Once the transceiver is negotiating, you will see the white 10GbE light on the UDM-PRO / UDM-PRO SE and in the console GUI, it will show it negotiating as a 10GbE device which is expected. This transceiver takes an RJ-45 connection that is one of the respective speeds and converts it 10GbE so it can be seen by the SFP port which can only negotiate on 1GbE or 10GbE. Now it doesn't matter what speed the modem port is because the UDM-PRO will be able to talk to it. This is fantastic for anyone on a Fiber service that offers 2.5Gb or 5Gb service like ATT does now in my area. (I'm only on the 1Gb service...)
As of this writing, the Ubiquiti transceiver is running $65 compared to the Planet Tech media converter (outlined below) which is going for around $190
Scroll down to the Using the WAN2 port as the WAN Port section to learn how you can make the SFP port which is classified as WAN2, default as WAN1. It's essentially flip-flopping the WAN1 and WAN2 physical ports from RJ45 to SFP.
Around November 2021, AT&T opened up for fiber internet in my area. Naturally I wanted the full duplex 1000Mbit over Cox Cables offering of 940Mbit x 35Mbit, so I made the switch. The Zyxel USG gateway I had at the time couldn't handle the new bandwidth with the SPI Firewall (or so I thought... different story) so I picked up the Ubiquiti Dream Machine Pro (UDM-PRO) since they claim the SPI firewall can handle up to 3.5Gbit of traffic on the WAN port. I got the new UDM-PRO, hooked everything up and was happy to have a new appliance to play around with that is easier to manage than the Zyxel (or so I thought... again, different story).
With the new UDM-PRO and the new AT&T modem, I naturally started poking around at the interfaces and noticed on my AT&T modem that it was connecting at 10000 Mbit. I figured it really meant 1000Mbit since that's the service I'm paying for and moved on. But it kept creeping back into my mind that I might actually be connected at 10Gbit... "Is this too good to be true?" I thought to myself and wanted to dig in and find out first hand. This is where I started running into all sorts of "fun" trying to get things to jive.
When I picked up the UDM-PRO, I also grabbed the SFP RJ45 10G Module to have on hand. Having very little hands on experience with SFP modules in general, let alone 10G networking, I stuck the 10G SFP into the WAN2 port on the UDM-PRO and plugged a cable into the 5Gbe port on my modem fully expecting the 10Gbe SFP card to auto-negotiate on the 5Gbe port. Nothing. The UDM software didn't even show anything was hooked up. I tried the 2.5Gbe port. Still nothing. Finally I popped into the GUI to force auto-negotiation which is where I noticed there are only two options for the 10Gbe port speeds and they are 1Gb or 10Gb. This led me down the rabbit hole of trying to find out if the 10G SFP+ port could even connect to my modem and the internets with all their wisdom informed me that it in fact can not negotiate on speeds outside of 1Gb or 10Gb.
Disappointed, I left well enough alone and gave up. A few weeks went by and I just couldn't shake the thought that I "might" have more than 1000 Mbit. I mean really... If you were paying for 1000 and thought there was the slightest chance you might be passing Go, collect 10000Mbit, wouldn't it keep you awake at night? A few more weeks went by and I started digging in to see what it would take to convert one of the four 2.5Gbe or even the one 5Gbe port on my modem over to the 10Gbe SFP+ port on the UDM-PRO.
This led me down a handful of rabbit holes, mostly where folks suggested getting a switch that could negotiate on the various speeds but I didn't really like the idea of wasting a perfectly good switch on this idea. Finally, I ran across the Planet Tech XT-705a Media Converter. This is a device that is designed solely for the purpose of converting 10Gbe SFP+ ISP connections to RJ45 Network connections. You read that right. It is advertised to go from the ISP fiber connection to an RJ-45 network. Nothing in their documentation (that I could find) says anything about going in reverse. It's kind of implied, but not out-right stated. I was kinda bummed since I didn't know if it would actually work or not, so I kept looking and after finding some really cheap looking made units on eBay that ship from China, I decided to take the $180 plunge and try out the Planet Tech XT-705a media converter anyway.
I picked up the XT-705a over on Newegg for around $185 and also the Ubiquiti Uc-Dac-Sfp+ Direct Attach Copper Cable Sfp+ 10Gbps 0.5 Meter for roughly $24. Total with shipping and tax was $211.
When they arrived, I think I expected more from the XT-705a but it really is pretty underwhelming. You get the unit and power cable. It's a really straight forward unit.
The UC-DAC-SFP+ cable has a quality build feel to it which is kind of expected coming from Ubiquiti but at a price point that is hard to beat considering individual SFP fiber cards can run $25+ and $60+ for RJ45 cards. (Planet Tech wants $165 for their RJ45 SFP+ module...)
Product details aside, I hooked everything up and got a green light on the Media Converter. At first, I thought the dots on the side of the RJ-45 port would light up telling me what the negotiation speed was. Nope... those are just painted on dots. I felt kind of dumb but it did have a green light on the right and that means it is connected at either 5G or 100M.
I don't know why but I didn't expect it to work. Or I expected to have to reboot stuff. Before digging in, I checked the internet on my phone and it went through no problem. I figured maybe it was routing through the cell internet so I hopped on my desktop and poked around on some websites but everything popped up just fine. I finally decided that since the device is a non-managed unit it, doesn't require a bunch of boot up time to work. If the light is lit, it's working and there literally isn't anything to it outside of plugging in the cables and power.
Next I decided to start checking the UDM-PRO and the AT&T modem to see what they were negotiating for speed. The UDM-PRO showed the SFP+ WAN2 port in use and negotiated at 10Gb and the modem showed that the 5Gb port had established connection.
Unfortunately when doing a speed test, I never did end up with the 10Gbit speeds I was hoping for. I get around 980Mbit DL but I've seen as high as 1200Mbit on the UL. I haven't decided if the speed test site that the UDM-PRO uses isn't trying to handle faster speeds but since nothing else in my network is faster than 1Gbit, I can't really play around with different speed tests to find out. Oh well. Since my modem can handle up-to 5Gbit speeds, I also wanted to future-proof my network so when the day comes that higher speeds are available to the modem, at least the pipe can handle it. I'm sure I'll upgrade some other stuff over the next few years but for now, I have a UDM-PRO that can eventually handle up to a 5Gbit ISP connection.
Oh, and if you have the UDM-PRO SE, this same method will also work even though the UDM-PRO SE RJ45 WAN port can negotiate at 2.5Gbe. (Seriously... why not 5Gbe Ubiquiti??)