Intro #
A year or two back I switched from a traditional all-in-one home router, the ASUS RT-AC88U, to a more “prosumer” setup, using a separate router, switch, and Access Points (APs). Unfortunately, when planning my Wi-Fi design I overestimated the range of the two UniFi U6-LRs I purchased. This left one room, which was located on the edge of my house, directly between my APs, with poor Wi-Fi signal. For a while the deadzone wasn’t too large an issue, but when my sister decided to use this room as an office, doing frequent video calls as well as using her laptop, phone, and tablet, all connected to Wi-Fi, the problem became much more pronounced. Today I’m going to patching up this weak point in my wireless network by using my old consumer router as an AP, configuring it with the same SSID as my other APs for seamless client roaming.
How this will work? #
This problem has been ongoing for a little while, and honestly I didn’t consider this solution until recently stictly due to me misunderstanding how Wi-Fi roaming works. I thought the process of a wireless client switching from one AP to another (roaming) was in some way handled by the APs communicating with one another to hand off the client. Because of this misconception I thought that I couldn’t have seamless client roaming across the same SSID when using APs from differing brands. In reality, it is the client that makes the decisions regarding when to roam from one AP to another. When a Wi-Fi client’s connection to its current BSSID (the service set an individual AP provides) becomes too weak it will search for other BSSIDs (other APs) that are part of the same Extended Service Set (ESS - a term encompassing all APs on the same network advertising an identical SSID & authentication). If the client finds new candidate BSSIDs it will authenticate & associate with the one it has the best connection to, then end the connection with the previous AP.
If that somewhat technical explanation was confusing, here’s the short and sweet version: If multiple APs on the same network are configured with the same SSID name and authentication, Wi-Fi clients can switch between them seamlessly. The important thing here is that wireless clients’ experience will be the same roaming between my UniFi APs and my old router in AP mode.
Configuring the router #
The first step to configuring my router as an access point was getting it connected to my current network. Since this project was still in a proof-of-concept phase at this point, I just ran a spare ethernet cable from my main switch across the floor to the office. If I do decide to keep this as a more permanent solution I’ll find a way to run a cable more nicely later. From here I connected the router to power and plugged in the ethernet cable to its “WAN” port. I used the WAN port since the router was currently configured to act as an all-in-one consumer router, and I didn’t want it to start fighting OPNsense as the main router on my main network (making DHCP offers and such). I actually found an ASUS article that says to plug into a LAN port when using one of their routers in AP mode, but I never switched it and it didn’t cause any trouble.
After getting the soon-to-be AP plugged in, it recieved a DHCP lease from my router, which I set to a static mapping so it wouldn’t change, and so Unbound (my DNS server running on OPNsense) would automatically create a DNS registry for it. From here I was able to access its web interface to configure it.
Firmware Update #
The first thing I did was update the router’s firmware. I didn’t see anything too intriguing when skimming the release notes for the firmware updates between the one I had and the latest, just lots of security patches, good to have nonetheless.
Getting to AP Mode #
The next thing to do was switch the router to AP mode. I did this by going to Administration > Operation Mode > Access Point Mode. After doing this and configuring the SSID to the same settings as my UniFi APs (under Wireless > General) my wireless clients were roaming to and from it when entering and exiting the office.
Wi-Fi bands and channels #
Even though my AP is now working, I’m not done configuring it yet. With this AP being nestled between my two other APs the overlap in service area is going to be even greater than before. Because of this, if I have APs on conflicting channels they could definitely cause issues.
On the 2.4GHz band I have my 2 UniFi APs running on channels 1 and 6. Since 2.4GHz channels 1, 6, and 11 are non-overlapping I could just stick this new AP on channel 11 and avoid any Wi-Fi interference. The only problem with this is that I’m planning on implementing a zigbee network soon, which will also operate in the same 2.4GHz space as Wi-Fi. Because of this I want to leave the top of the 2.4GHz space available for my zigbee network to ensure it doesn’t deal with any interference, eliminating Wi-Fi channel 11 as an option.
While I could change the channels for my UniFi APs, alternating between channels 1 and 6 for the 3 APs, the solution that fits my needs here is actually just not using the 2.4GHz band on this newly introduced AP. Since this AP is older than my UniFi APs, it doesn’t support Wi-Fi 6, so I want to steer clients away from using it unless it’s absolutely necessary. Because of this, the shorter range of the 5GHz band will actually be a benefit rather than a detriment.
Within the asus web interface I was able to choose my 5GHz channel under Wireless > General. I chose band 161 with a 40MHz channel width as this wouldn’t interfere with my existing APs’ 5GHz channels. Under Wireless > Professional I was able to disable the 2.4GHz band, as well as configure a couple useful settings on the 5GHz band to support my goal of limiting the usage of this AP.
First I enabled “Roaming assistant”, which drops wireless clients when their RSSI (signal strength) falls below a configurable threshold, forcing them to roam to another AP. This is useful to stop wireless clients from staying with this AP for too long when better options are availible, and as I’ve already established that’s pretty much anywhere in the house except the room this AP will be in. Because of that I’m starting with this set at -55 dBm, but I’ll update it as needed (normally clients won’t try to roam until their RSSI is around -70dBm or lower).
The final setting I changed was “Tx power adjustment”, a slider which I set to its lowest value, “Power Saving”. This setting just reduces the strength at which the AP transmits its 5GHz signals. Lowering this setting causes a quicker drop in RSSI as clients move away from the AP, thus promoting roaming sooner.
Conclusion #
Overall I’m pretty happy with the solution I’ve gotten to here. So far it’s working great, clients are using the AP in the office when needed, but are still prioritizing my UniFi APs most of the time. The only real downsides come from worsening the utility of the UniFi controller application I run in docker. Since wireless client information and configuration editing/viewing for the ASUS AP aren’t availible in UniFi controller, it becomes less reliable and less useful as a central tool for managing my wireless network. I knew this would be a consequence when I decided on this solution, though, and for me it’s worth saving the pretty penny another UniFi AP would’ve cost, their stuff is not cheap!