My mapped drive died on a Tuesday morning, right as I was trying to open a spreadsheet I needed for a call in ten minutes. Windows threw the classic "The network path was not found" error, and I spent five minutes convinced a drive had failed before I checked the router and saw the truth. My Synology had quietly grabbed a different address overnight.
That is almost always what is happening when your NAS seems to vanish. The box is fine. The address moved.
Here is why it happens and, more importantly, the exact steps to pin the address down so it never wanders again.
Why your NAS keeps grabbing a new address
Most home networks hand out addresses automatically using something called DHCP. Your router keeps a pool of addresses (say 192.168.1.100 through 192.168.1.200) and loans one to each device for a set period called a lease.
When that lease expires, or when the NAS reboots after a power blip or a firmware update, the router is free to hand it a different number. Your phone reconnecting, a smart plug waking up, a guest laptop joining: any of these can shuffle the deck.
The mapped drive on your PC, though, points at a specific number like 192.168.1.145. When the NAS becomes .150, the shortcut is pointing at nothing.
Two ways to fix it, and which to pick
There are two solid approaches. Both work, but one is far safer for regular home users.
| Method | Where you set it | Best for |
|---|---|---|
| DHCP reservation | Your router | Almost everyone. The router keeps handing the NAS the same address, and you cannot cause a conflict. |
| Static IP on the NAS | The NAS network settings | People comfortable with networking who want the setting stored on the device itself. |
The first time I set this up, I went straight for a static IP on the NAS and picked an address that was inside my router's DHCP pool. Two weeks later the router loaned that same number to a tablet, and both devices dropped off the network with an address conflict.
Start with a DHCP reservation. It is the method I now recommend to everyone, because the router stays in charge and hands out the same address every time with no chance of a clash.
Step 1: Find your NAS's current address and MAC
You need two things: the address the NAS has right now, and its MAC address (a permanent hardware ID that looks like 00:11:32:AA:BB:CC).
The easiest source is the router. Log in to it (the address is usually printed on a sticker, often 192.168.1.1 or 192.168.0.1), and open the connected devices or DHCP client list. Look for your NAS by its hostname, something like DiskStation, TrueNAS, or the model name.
On the NAS itself you can confirm the MAC too. On a Synology, go to Control Panel, Network, Network Interface and click your active LAN. On QNAP it lives under Control Panel, Network and File Services, Network. Write both values down.
Step 2: Create a DHCP reservation on the router
This is the fix that solves it for 90 percent of people. The menu wording changes by brand, but the idea is identical: you tie one address to one MAC.
- Log in to your router's admin page.
- Find the section named DHCP Reservation, Address Reservation, Static Lease, or Bind IP to MAC. On many routers it sits under LAN settings; on ASUS it is under LAN then DHCP Server; on TP-Link it is often under Advanced then Network.
- Pick your NAS from the device list, or enter its MAC address manually.
- Assign the address you want it to keep. I suggest a memorable one near the top of the range, like 192.168.1.10.
- Save, then reboot the NAS so it requests a fresh lease and picks up the reserved address.
After the NAS comes back, check the router list again. The NAS should now show the exact address you reserved, and it will keep that address through every future reboot.
Step 3 (optional): Set a static IP directly on the NAS
If your router is old, rented from your ISP, or simply will not let you create reservations, you can set the address on the NAS instead. This works, but you have to be careful about which number you pick.
First, look at your router's DHCP range. Say it hands out 192.168.1.100 to 192.168.1.200. You want an address outside that window, for example 192.168.1.20, so the router never tries to loan it to something else.
On a Synology: Control Panel, Network, Network Interface, edit the LAN, choose Use manual configuration, and enter the IP, subnet mask (usually 255.255.255.0), gateway (your router's address), and DNS (your router's address works fine, or 1.1.1.1). Save and reconnect. QNAP and TrueNAS follow the same pattern under their network settings.
Step 4: Repoint your mapped drives
Once the NAS has a permanent address, fix the shortcuts that were breaking. On Windows, open File Explorer, right click the dead network drive, and choose Disconnect. Then map it again with Map network drive and enter 192.168.1.10YourShareName, ticking "Reconnect at sign-in."
On a Mac, use Finder, Go, Connect to Server and enter smb://192.168.1.10, then drag the mounted share into your login items so it remounts automatically.
Update your backup software too. Time Machine, Hyper Backup targets, and any scheduled backup job that pointed at the old address needs the new number, or it will silently fail the next time it runs.
How to confirm it actually stuck
Do not just trust that it worked. Reboot the NAS one more time, wait about two minutes for it to fully come up, then open a command prompt or terminal and ping the address: ping 192.168.1.10. Steady replies mean the box is answering at the address you chose.
Then open your mapped drive. If the files appear without a password prompt or an error, you are done. I like to leave it a full week before I call it fixed, because lease conflicts sometimes only show up when a lease naturally expires several days later.
For a plain-language refresher on how automatic addressing works, Cloudflare has a solid explainer on how DNS and network addressing fit together, and Synology's own network interface documentation walks through the exact DSM menus.
When it still moves after all this
If the address keeps changing even with a reservation in place, three things are usually to blame. You may have two DHCP servers on the network, often because a second router or a mesh node is still handing out addresses; only one device should. The reservation might be tied to the wrong MAC, common on NAS units with two network ports where one is unplugged. Or the NAS may be set to "get address automatically" on a port you did not expect.
Sort those out and the address will hold. Once it does, that Tuesday-morning panic simply stops happening, and your drives, backups, and Plex library all keep working through every reboot without you touching a thing.
Frequently asked questions
Why does my NAS get a new IP address after a reboot?
When the NAS reboots it asks the router for an address, and if there is no reservation the router may hand out a different one from its pool. Your mapped drives point at the old number, so they break. A DHCP reservation ties one address to the NAS so it gets the same one every time.
Is a DHCP reservation or a static IP better for a home NAS?
For most home users a DHCP reservation is better and safer. The router stays in control, so you cannot accidentally create an address conflict. A static IP set on the NAS itself works too, but only if you choose an address outside the router's DHCP range.
What address should I give my NAS?
Pick something memorable and outside your router's DHCP pool, like 192.168.1.10 or 192.168.1.20. Check your router's DHCP range first, then choose a number below where the pool starts. Reserving it in the router avoids conflicts entirely.
My NAS still changes address even after a reservation. What went wrong?
Usually there are two DHCP servers on the network (a second router or mesh node still handing out addresses), the reservation is tied to the wrong network port's MAC, or the NAS has a second unplugged port. Disable the extra DHCP server and confirm you reserved the MAC of the port actually in use.
Will fixing the IP break my existing mapped drives?
The drives were already breaking, which is why you are here. After you lock the address, disconnect the old mapped drive and remap it to the new fixed number, ticking reconnect at sign-in. Update backup jobs to the new address too so they do not fail.
Do I need to set the same address on the NAS and the router?
No, and doing both can cause conflicts. Use one method. If you make a router reservation, leave the NAS set to automatic addressing. If you set a manual static IP on the NAS, do not also reserve that address in the router unless the numbers match exactly.
