10GbE without a new switch: direct NIC-to-NIC setup

Most 10GbE guides assume you're buying a switch. If you only have two machines that need the speed, a NAS and a workstation, say, you don't need one at all. A single cable between two 10GbE cards gives you the full 10 gigabits, and it skips the most expensive line item in the whole upgrade. This is the setup guide for that direct link: what it can't do, and how to configure it on Windows, Linux, TrueNAS, and Unraid.

What a direct link can't do

A direct NIC-to-NIC cable only connects the two machines on that cable. It's not a network segment anything else can join, there's no DHCP handing out addresses, and if one of the two machines needs to reach the internet or your existing LAN, it needs a second network connection to do that (its normal Ethernet or Wi-Fi stays in place and keeps doing that job). The 10GbE link exists purely for moving data between those two machines at full speed. If you later add a third device, you're buying a switch after all. This guide is for the common case where two machines cover it.

You don't need a crossover cable

This trips people up because it used to matter. Every 10GbE card sold today does auto-MDI/MDIX, which means it detects the wiring automatically and works with any standard Ethernet patch cable, straight-through or crossover. Buy a normal Cat6a (or better) cable rated for 10GBASE-T and plug it into both cards. There's no special cable to hunt for.

Setting static IPs

Without a switch, there's no DHCP server on this link, so both ends need a static IP address on the same subnet. Pick a range that doesn't collide with your main network, for example 10.10.10.1 on the NAS and 10.10.10.2 on the PC, with a /24 subnet mask. Neither address needs a gateway configured for this specific connection, since the link only talks to the other machine on the cable.

On Windows: open the network adapter settings for the new 10GbE card, set IPv4 to manual, and enter the address, a 255.255.255.0 subnet mask, and leave the gateway and DNS fields blank.

On Linux (desktop or general use): set a static address on the interface, either through your distribution's network manager GUI or with a netplan or systemd-networkd config file pointed at the 10GbE interface's name (find it with `ip link`).

On TrueNAS: go to Network, edit the new interface, switch it from DHCP to static, and enter the address. TrueNAS keeps this independent of the interface used for its main management access, so you won't lock yourself out by getting this one wrong.

On Unraid: the Network Settings page lets you assign a static IP to a secondary interface directly, separate from the primary management NIC.

Your normal Ethernet or Wi-Fi connection on each machine keeps working exactly as before. You haven't replaced it, you've added a second interface on a separate subnet, and the operating system routes traffic to whichever interface matches the destination address automatically. Traffic to the other machine's direct-link address goes over the 10GbE cable. Everything else, including your internet connection, keeps using the interface it always did. There's nothing to reconfigure on that side.

Confirm it's actually working

Once both ends have addresses, ping one from the other. A reply confirms the link is up before you move any real data. Then copy a large file and watch the transfer speed in your file manager or `iperf3` if you want an uncontested benchmark: a working 10GbE link should sit close to 1.1 to 1.2 GB/s for large sequential transfers, not the 100 to 120 MB/s a gigabit link would show. If you're seeing gigabit-range speeds instead, go back and check the PCIe slot the card is sitting in. Chances are it's not wired for enough lanes, and that bottleneck looks identical to a network misconfiguration from the outside.

Mounting shares over the direct link

Once the link is confirmed, point your file sharing at the new address specifically. On a NAS, that means adding the SMB or NFS share using the 10GbE static IP (10.10.10.1 in the example above) rather than the NAS's hostname, which would otherwise resolve to its normal LAN address and route your traffic over the slower connection instead. The same applies in reverse for anything the NAS pulls from the PC.

Every network card we stock names its controller (AQC113, RTL8125B, RTL8127, and the rest) right in the product title, so you know exactly which chipset and which driver you're getting before you buy. See what we stock, or ask us which card fits your build.