If you've been considering upgrading the backbone of your home LAN to 2.5GbE or even to 10GbE, know one thing in advance — it's not as simple as the switch to 1GbE was. However, that upgrade wasn't particularly trouble-free either, now that I think about it, which goes to underscore how important it is to plan your network upgrade in advance.
Upgrading to faster wired networking gives your home network much more bandwidth, which should translate to a snappier experience for you and your household. How snappier is a point of contention, because it depends on a multitude of factors, from the devices you already own to the new equipment, the quality of the installation, and anything that could cause interference. I've upgraded my home network to a mix of 2.5GbE and 10GbE, and even though I researched things, I fell into a handful of issues that I now know are more common than I thought.
Assuming all existing cables will work
It's probably time to throw out those old patch cables at the least
Whether you decide to upgrade to 2.5GbE or 10GbE, hardwiring as much as possible is going to give you the best experience once the upgrade is finished. And that can be a problem, depending on how long ago your existing network wiring was installed, and when your patch cables and other cables for Ethernet use were manufactured. Not every copper twisted-pair cable will be able to handle 10GbE, although most should be fine with 2.5GbE as long as it's not ancient wiring.
2.5GbE is going to be fine up to a few hundred feet using Cat5e or Cat6 wiring, for the most part anyway. You might run into issues if the existing wiring is damaged somewhere on the length, or if the terminations or wall jacks were of low quality. It's entirely possible you might not have noticed issues before, depending on the speed of your internet plan and whether you use wireless or wired networking more.
If you plan on using 10GbE over Cat6, you'll probably want to fish new wires through your walls and replace all the shorter cables between your network appliances. My advice? Throw away all the old cables as well, because you'll end up rotating them back into circulation otherwise, and then it'll be a fun day of troubleshooting trying to figure out why you have intermittent issues with your network. Even if you upgrade all your cables, I wholeheartedly suggest to invest in quality tools including a cable tester, because it'll save so many headaches.
Compatibility and auto-negotiation
Not every old device will be able to connect to faster ports
I'd almost forgotten how bad the old days of wired networking were, when not every NIC would auto-negotiate the correct speed with the other network hardware you were trying to connect it to. ALMOST, but that cursed knowledge came crashing back when I tried switching out my managed network switch for one that had mostly 2.5GbE ports and a couple of SFP+ ones.
There were two problems that hit me immediately. I had a few 10/100 Mbps devices like older smart home hubs that were fine on my old gigabit ports, but they wouldn't get a link connected to the 2.5GbE ones. Annoying, for sure, but I wasn't about to let it phase me and I added those to a small gigabit-only network switch for the time being until I could figure out a better solution, like upgrading the hubs to newer ones.
The other was that an older switch I had wouldn't connect at the intermediate speeds. 10GbE links were fine, 1GbE links were fine, nothing else. The problem is that not every older device is designed to auto-negotiate to the Multi-Gig speeds of 1, 2.5, 5, and 10GbE, and this was one of them. Easy fix, but an expensive one, to replace the switch with a modern, managed one with proper speed support.
Oh, and some driver issues with two of my Windows 11 PCs, which also didn't like staying connected at anything faster than 2.5GbE. Annoying but not dealbreaking, and I could always add a PCIe NIC at some point to get the higher speeds.
Underestimating power usage
And heat generation is going to come into the picture in a way it never had before
One thing I know you won't have thought about, because it came as a shock to me, is just how much heat 10GBase-T ports generate. I'm talking too hot to handle without gloves on here, significantly more than 2.5GBase-T, DACs, or fiber transceivers. That heat comes from one thing: power consumption of between two and five watts per port. So, that's more heat generated, more electricity used, and more cooling needed, making the net cost of running 10GBase-T higher than other options.
Using SFP+ or DAC connections could be under a watt per port, and if you live somewhere with high utility costs, that's going to be a much better option. 2.5GBase-T is nowhere near as hot or power-hungry, so don't worry too much there.
Expecting immediate results
Your storage solution might be the bottleneck, not your network
I recently added 10GbE networking to several segments of my home network, and it's not the panacea you might have envisioned. My network is faster to use, but some of that is from wiring more devices, so there's more airtime on my Wi-Fi for things that can't be wired. It's also more stable when doing large file transfers and snappier when browsing my two NAS devices.
Those file transfers weren't that much faster, though, at least not to the larger NAS I have that uses large-capacity HDDs. The all-flash NAS was a different story, and could use every bit of the 2.5GbE link that it supports. I do love seeing the file transfer window on my PCs for less time than before, and some services felt faster to use but that could have been my mind playing tricks on me. But overall, the upgrade to faster wired networking is forward-planned, so that I have the capacity when my ISP increases its offering past Gigabit, or for the ever-growing number of devices connected to my network.
Driver and operating system issues
Windows and 10GbE is a particularly problematic pairing
I've got a mix of client devices on my network, and the majority of them never have any networking issues at all. But, I only have a few Windows-based devices at home, and those are the ones that give me the most trouble. Aside from Wi-Fi woes, the recurring thread for my network is trying to connect at faster than gigabit via Ethernet.
Whether it's driver issues, conflicts after operating system updates, sleep and resume bugs, or even the occasional non-booting system, Windows is a pain to use with 10GbE connectivity. Linux and FreeBSD-based clients I own only have issues with Realtek NICs, so anything *nix based gets the good Intel NICs, and the Windows machines get whatever is left.
To be fair to the newer motherboards and PCs I own, they have been flawless when they have 2.5GbE NICs. It's the 10GbE Aquantia ones that are the problem, so keep that in mind if you're upgrading. It might be a good plan to get PCIe network cards to add to PCs that have an empty slot to use, and then you are less likely to get issues overall.
Switching to 2.5GbE or 10GbE is worthwhile, but don't get caught out
Having Multi-Gig home networking is a fantastic investment, but that also means it deserves a proper plan to get started. Part of that process is finding out which things might turn into blockers or will cause issues down the line, and all of these issues qualify. I'm sure I've missed some, these are ones that I've either seen repeatedly on forums or ones I've personally experienced, and the field of networking is vast enough that there's going to be others I've not heard of.