What happens if two networks have the same SSID and password?

Question

Related to this question: What happens if 2 wifi networks (run by different people) have the same SSID?

BUT in my case both WiFi have the same password.

I have two cases to consider:

1. If they are broadcasting in the same location, what will happen?
2. If they are in different locations, will devices which know about WiFi A automatically connect to WiFi B?

I'm setting up a WiFi using a MiFi dongle for use on vacation and wondered if I set it up the same SSID/password as my home Wifi, if I can save everyone having to add a new Wifi to all their devices... which these days is quite a large number!

Is SSID/password all that identifies a WiFi network to my PC or would different security settings mean it is not seen as the 'same' network?

Answer 1

Two identically named SSIDs with the same password will allow your device to connect to either, without having to add any extra networks on your devices.

If both routers are broadcasting from the same location, the expected behaviour will vary depending on device. For example, some devices will connect to whichever router has the stronger signal, others will just connect to the first router they "see".

Answer 2

The other answer here is technically correct on "it will allow your device to connect to either (if both of them are broadcasting from the same location)", but there is a subtle detail here and the actual result is probably not what you hope 2 same SSID would do in the first place. The actual outcome is: Your devices do not seem to be able to roam between the 2 SSID networks!

Data source: my own experience with some devices from named brands.

My setup:

1. I originally also setup 2 WiFi routers (one is actually creating a downstream sub-network within another). Both have identical SSID+password (and same 2.4GHz frequency, for that matter), at upstairs and downstairs in my house, in hoping that they would be seen as same network, thus allowing my devices to freely roam from one to another, whenever they see fit (hopefully based on signal strength).

2. Such setup seemed to work in the way I expected, in a sense that all my phones, tablets and computers show only one available WiFi network, rather than two with same names. My devices can connect to that network, and work just fine.

3. But, in hindsight, my devices displaying only one SSID network might just mean they silently hide the other one with the same SSID; it does not necessarily mean these devices can roam between both. In everyday usage, you just won't know. A device might just be sticking with one WiFi network all the time.

4. How/when did I realize things weren't right? Recently I happened to disable my downstairs router, and then I found out a certain set of my devices became offline. In their network setting menu, there is still one seemingly same WiFi network as a "remembered network" meaning the device does have the password, but tapping the "Connect" button would always fail. Realizing what was happening, I can experimentally re-enable my downstairs router and disable the upstairs router, now my previously unable-to-connect devices can work, but the another set of devices would become offline.

The conclusion: Setting up 2 WiFi networks with same SSID+password is not the "poor man's mesh WiFi" that I hope it would be.

Answer 3

I know that an iPhone 12 will allow an identically named network (with or without security) to connect and replace an operating network if the device being managed is configured to allow it to connect. Hidden or not, the newcomer can displace the running network if appropriately configured. I can supply screen shots of two identically named networks waiting to connect to my wifi. Usually the intruder is hidden (not broadcasting its ssid), because that's how wifi hacks begin. The intruder doesn't need the legit password, by the way.