A second Ethernet port is fairly common among NAS devices. Even affordable options usually come with two ports, often 2.5GbE or faster. While you could spend a lifetime without touching the second port, there's a breadth of useful features that open up once you plug a network cable into it.
Link aggregation
Keep your connection stable during rush hour
Link aggregation is the first thing everyone should look into if their NAS comes with two Ethernet ports. Now, plugging in two network cables won't magically double your transfer speed in most real-world scenarios, but it can help keep the connection stable and fast when multiple devices are accessing the NAS at the same time.
Adding a second cable effectively gives your NAS "highway" an extra lane. You won't double bandwidth for a single client, but you can improve total throughput across multiple clients. For example, if you use your NAS for both backups and media streaming , one device can transfer files while another streams video without congesting the connection.
If you have a simple setup consisting of a single client and a NAS, link aggregation probably won't make a difference. But if your household is chock-full of devices constantly accessing the NAS, using both Ethernet ports can be a godsend. Just note that proper link aggregation typically requires support for LACP (Link Aggregation Control Protocol) across the entire chain (NAS, network switch , and router), and that you'll likely need to spend some time testing and troubleshooting.
Redundancy
Having a fail-safe is always handy
Jordan Gloor / How-To Geek
If you don't need extra bandwidth, you can configure the two Ethernet ports to run in failover mode. This way, if one of them fails or something else happens to it, your NAS will stay online because the second port automatically jumps in and keeps the lights on.
While link aggregation may be overkill for simple setups with just a few devices, redundancy can still be very useful even if you only have a single client, because your backups can continue uninterrupted even if one of the Ethernet links goes down.
Connect two NAS devices with a separate link
Isolate your backup NAS while keeping it connected to the primary device
Patrick Campanale / How-To Geek
If you use two NAS devices (one primary and one for backup), you can use the second Ethernet port on the primary NAS to connect it directly to the backup unit. This allows you to keep the backup NAS on a separate subnet or isolated network, while the primary NAS remains connected to both your main network and the backup link.
From a security standpoint, this can be a smart approach. If your primary NAS is compromised via the main network, the backup NAS is less exposed since it isn't directly accessible from that network. If the backup NAS also has two Ethernet ports, you can dedicate one to the isolated link and use the other for managing the NAS. When you're all done, just disconnect the cable, and you're golden.
Reserve one port for management access
Keep one lane free for maintenance
Jordan Gloor / How-To Geek
That second Ethernet port can be useful even if you don't need extra bandwidth or don't have a backup NAS. For example, you can dedicate it to management access, allowing you to reach the NAS even when the primary link is congested.
Separating storage and services is another option if you're using your NAS as a media server or for self-hosting. For instance, you can reserve one port for general file access while using the second for services like Plex or Home Assistant.
Use the second port for a direct connection to a client
Establish a fast, dedicated link with your PC
Jordan Gloor / How-To Geek
If you own a PC and a NAS with two Ethernet ports, you can connect them with an Ethernet cable. This can be handy if both the PC and NAS have 2.5GbE or faster ports, but your network is limited to 1GbE.
A direct connection allows you to achieve higher transfer speeds between the two devices while keeping the NAS connected to the rest of your network for other clients. This way, other clients will be able to connect to the NAS and do their own thing without compromising the transfer speeds of your primary machine, and vice versa. Just make sure to use two Ethernet ports that have the same speed. If one of the ports runs at 2.5GbE and the other at 1GbE, the connection will fall back to the lower speed.
You'll also need to properly configure networking, so the two devices automatically use the fastest available connection. You can usually do this by assigning static IP addresses to the direct link and connecting via that IP, but in some cases, you may need to adjust routing metrics or modify the hosts file.
Keep some of your devices separate from your main network
Prevent your IoT devices from accessing your home network
Homey
A good chunk of IoT devices lack built-in security features, making it risky to let them access your main home network freely. Keeping them on a separate subnet is a much safer approach.
If you run your favorite home automation platform on your NAS, you can use its two Ethernet ports to separate your main network from the subnet reserved for smart home devices. This allows your automation software to communicate with IoT devices while still letting you control them from your phone or PC, while keeping the smart devices separate from your main home network.
Similarly, if you have a self-hosted security camera setup on your NAS, you can route camera traffic through the secondary Ethernet port and keep it isolated from your main network. This is a more niche use case, but it can be useful in case you have multiple cameras outside and are concerned that someone might yank off their cable and access your home network.
Keep that second Ethernet port busy
You should use the second Ethernet port on your NAS even if your setup is fairly simple. If nothing else, running them in failover mode will ensure your connection remains stable, no matter what happens to one of the ports.
The chances of a port or cable suddenly failing are minimal. But if the impossible happens—and it usually does at the worst possible moment—you won't be able to stop congratulating yourself for setting up redundancy.
