Wondering how to adopt UniFi Ultra switch without SSH? Seeing SSH Connection Reset by Peer? – in this guide we’ll provide 3 Remote Adoption Workarounds.
If you’re hosting a UniFi controller — either the older Network Application type or the newer UniFi Server OS — and you’ve tried adopting an Ultra switch (e.g. USW-Ultra, newer Flex Mini refresh, some Lite Gen2 refresh models) through SSH, you’ll likely have hit the issue where the switch flat-out refuses SSH.
You’ll see:
kex_exchange_identification: read: Connection reset by peer
Connection reset by x.x.x.x port 22
Previously, as long as you sat on the same network, you could adopt via Layer 3 using the mobile app and then move it across using set-inform.
That workflow has now gone.
So if your UniFi Ultra won’t adopt to a remote controller, or you’re seeing UniFi Ultra SSH not working, what are your options?
Below are three tried and tested methods that actually work when adopting a UniFi Ultra to a hosted controller.
1. HostiFi Discovery Tool (Recommended)
This is the easiest option by far.
Download the free HostiFi Discovery Tool, connect your laptop to the same local network as the switch, discover it, and insert your inform URL or controller IP address.
That’s it.
We use this as our go-to method when doing remote UniFi Ultra adoption to hosted UniFi OS servers.
It’s:
- Free
- Fast
- Doesn’t require DHCP access
- Doesn’t require DNS changes
- Doesn’t require SSH
- Works on Mac, Windows and Linux
The only negative from my side is that you need to manually type the inform URL rather than copy/paste it — but honestly, that’s a minor inconvenience compared to wrestling with SSH that simply won’t open.
We have no affiliation with HostiFi (they’re technically a competitor as we also offer controller hosting), but this tool is absolutely worthy of a link.
If you’re currently searching for:
- UniFi Ultra refusing SSH
- UniFi Ultra remote adoption
- USW Ultra cannot set-inform
- UniFi Ultra not showing in controller
Start here.
2. Local Controller (Old-School Bootstrap)
This one works, but it’s a bit clunky.
Install a local UniFi Network Application on your laptop or PC, connect to the same network as the switch, and adopt it locally.
Once the switch shows as Connected, SSH into it and run:
set-inform http://your-controller-ip:8080/inform
Run it twice.
Then jump onto your hosted UniFi OS and adopt it there.
Finally, go back to your local controller and Forget the device so it doesn’t try and reclaim it later.
It works — but I don’t love it. There are too many steps and I don’t really want a controller running on my laptop just to get around a UniFi Ultra SSH connection reset by peer issue.
3. DHCP Option 43 (Proper Network-Level Fix)
If you have access to the router handing out DHCP and it supports custom DHCP options, this is the cleanest “infrastructure-level” solution. I’ve not personally tried this option, and I’ve seen mixed reports, but it may be worth a try if the two above don’t work.
Ultra switches now expect to discover a controller during boot using:
- Layer 2 discovery
- DNS entry (
unifi) - DHCP Option 43
If they don’t, they won’t unlock SSH or accept a remote inform.
So you can point them at your hosted controller automatically using DHCP.
Step 1 – Convert Your Controller IP To Hex
Let’s say your hosted UniFi OS lives at:
89.167.53.0
Convert each octet to hex:
| Decimal | Hex |
|---|---|
| 89 | 59 |
| 167 | A7 |
| 53 | 35 |
| 0 | 00 |
So your hex IP becomes:
59:A7:35:00
Step 2 – Add UniFi Discovery Prefix
UniFi requires the controller IP in this format:
01:04:<HEX-IP>
So your final DHCP Option 43 value becomes:
01:04:59:A7:35:00
Some routers want this without colons:
010459A73500
Step 3 – Add Option 43 To DHCP Server
Now add the following to your DHCP configuration:
| Option | Value |
|---|---|
| 43 | 01:04:59:A7:35:00 |
Factory reset the Ultra switch after applying this.
When it boots, it will automatically discover your hosted controller and appear as:
Pending Adoption
in your remote UniFi OS.
No SSH required.
Final Thoughts
If you’re trying to adopt a UniFi Ultra to a cloud controller and you’re stuck with:
- UniFi Ultra SSH not working
- UniFi Ultra cannot set-inform
- UniFi Ultra connection reset by peer
…it’s not you.
The legacy SSH adoption workflow no longer applies to these newer models.
Your best bet for fast staging on ISP or 4G routers with no DHCP control is to run a local discovery tool, bootstrap the device once, and then move it to your hosted controller.
It takes about two minutes per switch — and saves a lot of head-scratching.
Author: Huw Jones – Home Network Solutions Berkshire
Huw is a UniFi specialist and the owner of Home Network Solutions Berkshire, providing professional networking, CCTV, gate automation and smart home installations across the UK. With years of hands-on experience and a growing YouTube audience at @home.network.solutions, Huw creates practical, no-nonsense guides to help homeowners and installers get the best out of their UniFi systems.
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