Mission Impossible: Replace existing router with Ubiquiti USG

I've been a home router hobbyist for a while now.  Probably goes back to my college days where I was pretty sure I was going to get a Cisco certification.  Careers took me a different direction.

I've run stock, tomato, wrt, pfsense, edge, and now I'm giving a USG a shot.

That USG sure wants to be set up fresh on a new network.  If you're like me, you already have a lot of in place gear and your own subnet setup that you don't want to mess with.  I was able to replace my existing non-Ubiquiti router without having to detach anything other than the router.

I have some Ubiquiti gear on my network, so I was already running the controller software on a desktop PC.  I'll tell you what, that USG sure didn't want to adopt.  This is what I did and it ended up being easy, just took a while to figure out.  In the end, I was as able to adopt all the hardware and not lose my existing Ubiquiti controller setup.

Materials:

• Desktop running existing controller
• Laptop running a fresh install of the controller software for windows (or your OS of choice)
• USG
• Network cable

I recommend updating the controller software to the latest version so you're running the save version on both computers.  The second computer doesn't have to be a laptop, but it makes it easier to keep track of the computers for descriptive purposes.

1. Don't take any gear apart yet, you're going to want internet for the following steps
2. Make a backup of the existing controller software on the desktop.  That can be found in Settings > Maintenance.
3. Copy that backup to the laptop
4. Turn off wireless on the laptop and disconnect all other network cables to the laptop
5. Restore the controller backup to the laptop (you might have to do some initial config beforehand)
6. Connect the laptop with the network cable to the LAN1 port on the USG
7. Setup the Settings > Networks so that it mirrors your existing network's DHCP config
8. Adopt the USG on the laptop
9. Backup the laptop controller config, name the file accordingly
10. Disconnect the laptop from the USG and put it back on the existing net
11. Transfer the new backup to the desktop and restore it
12. Swap out your old router for the USG
13. Give everything a restart for good measure

I was getting hung up on the fact that the USG REALLY wants to be 192.168.1.1.  You can't adopt a ubiquiti component that is on a different subnet.  By hooking up the laptop, it uses the USG's DHCP and the USG can be adopted.

This worked for me and I'm enjoying the USG so far.