If you've taken the plunge and upgraded to multi-gig networking, you might have noticed your data transfer speeds don't seem to match up with the advertised port speeds of your router, switch, and computer. It can be quite a shock to see your 2.5GbE equipment not behaving as you thought it would, but I can assure you that for the most part, your new networking equipment is probably working as intended.

That's perhaps not quite what you wanted to hear, but it's the truth. Even in ideal, laboratory conditions, these devices might not match their rated speeds, and that's okay. If you're seeing wildly differing values from the port speeds and your internet package's rated speed, then it's time to do some troubleshooting. Still, as many networking issues are on the physical layer, it's often a simple fix.

Networking speeds are *always* a best-case scenario number

Just because the lab says it can that doesn't mean you can

There are a few common misconceptions around wired networking, and one of them is that the ports' negotiated speed will be the speed you'll see in practice. In reality, if you add a 2.5GbE switch to your network, that 2.5GbE number is the maximum you'll get, and every single part of your network is working against you to make that number go down. If it helps, the same frustrations also plague network professionals, so you're all in the same (sadly sinking) boat.

Your data transfer speeds across your network will only be as fast as the slowest component in the chain. Most of the time, that will be the hard drive or SSD in your PC or NAS, or the speed of the internet package you get from your ISP. Sometimes it's because your network switch lacks the processing power or backplane bandwidth to handle the number of connections or amount of data transfer, but that's more expected in a congested networking environment and not in your relatively quiet home network.

Sometimes it's due to misconfigurations, like bufferbloat where undersized buffers cause dropped packets during congestion, and oversized buffers cause latency at any time. It could be a physical issue, like a damaged cable, one that's not plugged in fully, one that's not working as full-duplex for whatever reason, or a failed auto-negotiation to the 2.5GbE speed you expected. And yes, it could be a firmware or hardware fault with your networking hardware, although this is less common.

Some features will cause slowdowns when enabled

Multiple advanced networking features can slow down your network when in use. Security features are the first thing I'd check, like stateful firewalls using packet inspection. These will be rated with a pass-through bandwidth to check before purchasing. For example, many preconfigured hardware firewalls that Deciso, OPNsense's developer, sells have a 10 Gbps firewall. VPN usage is another culprit, with older protocols like IPsec limited to 1.2 Gbps, while WireGuard and other new protocols can handle faster speeds.

So, what can you do to get the best network speeds possible?

You can do a surprisingly large amount without spending a cent

The first thing to check if you're experiencing network slowdowns is every physical connection, so they're all appropriately seated in the ports, and there isn't any visible damage to any cables. Setting Quality of Service in your router's settings will help if the slowdowns are due to file transfers or other network activity that doesn't need to be done at high priority. Sometimes, a simple reboot of your router and other network appliances can fix many issues, including slowdowns.

Your router and other hardware generate heat, so controlling their thermals with adequate airflow or cooling methods is essential for peak performance. Staying on top of firmware and software updates can also help, I've had several routers that only managed to pass through half their available port speed to the Wi-Fi network due to firmware bugs that eventually got patched. And setting up network monitoring for visibility of your network's baseline performance and potential issues will help you understand what's happening.

But you might need to upgrade some hardware

Some issues can only be fixed by opening your wallet, like replacing low-quality cables. Go for Cat6 or Cat6a. Aim for all-copper instead of copper sheathing, look for wire gauge 22 or 24, and also for certified stamps like EIA/TIA. It's unlikely that Cat7 or Cat8 will be sold in general marketplaces, so avoid those. There is a massive market for fake cables, which will worsen your issues. Prosumer or enterprise networking gear is more likely to give you closer to the advertised speeds, but you will pay extra for it, so it's a question of whether that has enough value for your needs.

Remember, 2.5GbE is a theoretical negotiated speed, not a guaranteed one

Those 2.5GbE ports on your network switch promise what could be, like a single-family house in suburbia with a white picket fence, or the food you see in fast food advertising. It's rare that it's that good in practice, but at least your network speeds should resemble the ones your hardware was advertised for. Any large deviation from that and it's clear something isn't quite right, and some troubleshooting is your next step. But even then, tempering your expectations slightly before any purchasing decisions will go a long way to getting a home network that you're happy with the performance of.