If you've got a growing internal network of services, you may well be finding some frustration in their constantly changing IP addresses. Luckily, there's an easy solution. You can use your router to configure static allocations for each of your network devices, keeping them from jumping around the DHCP range and constantly breaking connectivity between internal services, devices, and applications.

Let's go over some of the reasons why setting up static IP reservations can be a great thing for your network management, and debunk a few myths about some of the things that static IP reservations can't actually help you with.

Why should you set a static IP on your router?

Never lose your home services again

The biggest reason to map a static IP reservation on your router for your devices in the home is pretty self-explanatory - your devices will remain static. If you're running services in your home lab or NAS, the last thing you want to be wasting time on is checking which IP address your devices have been reassigned on a regular basis. Dynamic IP addresses on your network are assigned using DHCP (Dynamic Host Configuration Protocol), which gives each newly connected device an IP assigned from a pool, leased for a period of seconds. This lease can last anywhere from a few seconds to weeks, but after that time, there's no guarantee that your device will receive the same IP. Depending on your router, this can also change after reconnections or reboots of your devices or the router.

Setting a static reservation means that your devices will stay in the same place on your network, so they can be reliably contacted by other services and your devices. This also makes it easier to target if you're running DNS internally (or even externally).

Static IP reservations can simplify your router configuration

If you're planning on port-forwarding, we'd definitely recommend setting static reservations. This goes a little past convenience and starts to touch on your security. In an admittedly unlikely scenario, a port-forwarded device running some external service could be replaced by another device via DHCP (we're reaching here, but it is possible) running a service on the same port. This might sound super unlikely, but if you've got several internal services running on a common port (say, port 80/44 for HTTP/S), you could easily accidentally expose a service which was not configured for nor sensible to expose to the wider internet.

While unlikely, this is the kind of risk (and inevitable debugging hassle) that you can avoid by simply setting static IPs on your router.

The alternatives can be a pain

Setting static IPs on your router is far from the only option for managing services internally, and certainly isn't the most scalable one. In an enterprise environment, setting a long list of static IPs is the exact kind of high-maintenance practice companies tend to avoid. That said, for your home network, the alternatives can be a bit of a pain.

These alternatives tend to either fall into a hostname/DNS registration camp, or some other protocol for service discovery over the network. There are tools to allow Dynamic-DNS resolution internally, as well as protocols like Avahi and Bonjour, multicast DNS, DNS-SD and even UPnP. However, these tend to be difficult to set up.

One good alternative, however, if your router supports it, is mapping hostnames to devices. This allows you to use your device's MAC address to effectively set up DNS on your router, dynamically setting hostnames for your devices. Support for this is limited though, and you'll need a decent router. We'd recommend this option if it's available to you, and assuming you're looking to scale past static IPs.

Why shouldn't you set a static reservation on your router?

Now there are no real downsides to setting a static IP reservation. Yes, it can introduce some management and maintenance overhead, needing to log in to your router to make changes every time you spin up a new device, but we'd say it is worth it. There can be some frustrations with it as well. If you're an infrastructure-as-code nut like me, then having to do anything manually feels like a chore, but the hassle you'll save debugging missing network devices and connecting your services together will make it worthwhile.

That said, here are some old myths about what static IPs can't do for you.

Should you use static reservations to improve performance?

This one is decades old, but is a myth that still bounces around some corners of the internet. Yes, setting a static IP for your devices can simplify the work done to allocate traffic on your router and theoretically increase performance. It's incredibly unlikely that your router's performance is limited on a purely packet-switching level though (unless you're running an extremely sizable internal network), so the impact of a static route is going to be minimal anyway. Definitely don't expect to set some static reservations and magically resolve internal network issues. If you are experiencing network performance issues, we'd recommend using tools like Netstat, iPerf3, Traceroute and Nmap to troubleshoot.

Do static reservations improve your security?

For the vast majority of people, setting a static IP will have no significant impact on your security. Sure, there are some cases where you can improve your firewall configuration by setting static IPs, but this is an extremely niche scenario and if you're at that point, you probably don't need us to tell you what you're doing or why you're doing it. For everyone else, there's no significant security improvement to be found by setting a static IP, apart from the extremely niche case we mentioned earlier about reducing misconfigurations around port-forwarding or other exposed services.

Is it possible, even if your router doesn't support static reservations?

In the worst case scenario where your router doesn't support static reservations, it's not going to do any damage to set static IPs on your devices. Sure, it'll be a pain to manage and might cause DHCP conflicts if not configured correctly, but (despite what some on the internet might tell you) it's hardly a precursor to the downfall of all humanity. That said, we do recommend avoiding this scenario if you can, for reasons we'll outline below.

Static IP or IP reservation?

A final important distinction here is between a static IP and an IP reservation. We've used the terms fairly interchangeably here, but you might notice we've been clear to state "on your router." That's because configuring a static IP per-device is usually a bad idea, and one that can cause you headaches. You should instead configure your devices to receive a static IP reservation via your router, which has the exact same effect, but with significantly easier management and no risk of IP collision with DHCP allocated IPs.

The technical difference here is that your router is simply allocating the same IP every time when asked by your device for a DHCP lease, instead of your device bypassing DHCP altogether and just hoping that the network configured actually exists. There are some other benefits too - changes in your DHCP configuration to things like DNS servers will be reflected on all your devices without updating them individually.

It's important to understand the difference here - setting an IP on a device itself is generally not a good idea. You should be using your router's console to set an IP per device. Your router does need to support this, but most decent modern routers should have this as a core feature.

It's useful to know where your devices live

Regardless of how you go about it, generally on your home lab or internal network you need some way for applications to know where other services live. Even if you are using something like DNS internally, you still need static reservations to ensure that your internal addresses are resolving correctly. We don't recommend setting static IPs on devices, only on your router.