If a device is connected to a Wi-Fi network via WPS, will it stay connected if the SSID of the network is changed at a later date?

Question

I should start by noting that I'm aware of the known security risks with using WPS within a network setup; the following question is just for informational purposes.

Assume the following:

1. I have a router broadcasting an SSID (let's call it "Network_A")

2. Using WPS, I now connect a device to my wireless network

3. Finally, I change the SSID of my network from "Network_A" to "Network_B"

In this situation, will any devices that were previously connected to the original SSID stay connected - or as with connecting equipment by using a network key, will they need to be re-connected manually?

Answer 1

They will need to be reconnected manually.

This isn't a theoretical question or answer, they will disconnect as soon as they miss enough beacon/management frames from the access point. This behavior will be the same across all 802.11 capable devices. It's not that the AP has disappeared when you change the SSID, but it's identifying information has changed from the client view. (BSSID + SSID combination) and their perceived signal strength to the access point will be zero, as there are no longer beacon/management frames being received from the client, this means no RSSI (i.e out of range).

IP Addresses or their DHCP leases have nothing to do with keeping a 802.11 connection alive. Wireless access points work at Layer-2 of the OSI model, or the "physical/link" layer-1 of the TCP model.

Most, (if not all?) Operating system wireless network profiles are based on the SSID. So the client devices will see the new SSID as a whole new network, and thus you will have to reconfigure the clients with the new network credentials.

Answer 2

When you connect to a WIFI network through SSID and password and you remember those credentials, you will automatically connect to networks that match these SSID and password combination (assuming the password is correct, of course).

When the SSID changes, you basically change the username of the combination. Your WiFi connection will remain connected until the lease expires. The problem is, that in order to alter the SSID, the wifi transmitter needs to restart its services, which automatically drops all connections.

If you can ADD an SSID to the group (enterprise WIFI accesspoints can do this), and you then REMOVE the old SSID, the services do not need to restart, in which case existing connections will remain alive until their lease expires in which case they need manual config to work again.

That said, according to Tim Stewart, your connection will drop because their received signal strength index (rssi), is based on the beacon interval (10x) a second usually. Once the beacon/management frames disappear, so will the clients association. Was unable to verify this, but added it into the answer anyway. Will change the answer once I can verify.

Because the SSID is no longer the same as what you connected to earlier, any device that was previously connected will not connect back to the new network. If you choose to rename the SSID again, back to what it was before, all devices will reconnect back to your device when it performs its next scan, which can be as quick as 1 minute or less, or more depending on that device.

You can compare this to having an email address with password. If you change the email address, you can no longer login to get new emails as the email address is also the login name. If you go into your email account settings, and you alter the login name to the new one, you can connect again. This is basically what happens in your scenario.

Answer 3

Short explanation:

Yes, once you change the SSID all existing connections to that SSID get dropped and have to be reset with the new SSID and "reconnected" manually. This is because usually your your AP will drop all connections after making significant changes to the configuration. Although it depends on make and model - a different implementation will result in different behaviour: cheap devices (with multi SSID) will drop all connection for all SSIDs better ones will drop only the ones connecting to that specific SSID.

Long and detailed practical explanation:

A general/abstract explanation in layman's terms would go like this (Note: this depends on the actual implementation - and I never developed an AP and I just deduct this from my general development knowledge on how embedded system work in general):

The SSID will be saved somewhere on a persistent flash memory and that is what you access and overwrite when you change it. Re/Starting the AP will result in the value being "put" from flash into the AP's RAM from where it's being utilized for the AP's actual operation. This means changing the value during operation wouldn't do anything since you would just change the value on the flash memory which will not be used until the AP restarts. Of course in reality the AP "knows" that you changed the setting and takes steps to apply them. It will restart it's operation thus dropping all existing connections. Since "live updates" are more costly to implement and there isn't a use case to your scenario the programmer wouldn't bother changing the flash and RAM value when changing the settings. Why should he, when "restarting" has the same result (not restarting in a way you would through the GUI just restarting the "service" running on the AP).

Alternative answer with a long and detailed theoretical explanation:

Back to your question: Assuming your AP doesn't drop the connection actively when you change the SSID and just "uses" the new SSID instead of the old one, I think it could work but I'm not completely sure. So in this case no, you wouldn't have to reconnect manually.

Note, the following explanation is theoretical (and not within the scope of Superuser, since it's not about a "real" HW or SW problem):

The SSID is required for the authentication and association process. Once the session is completely established (not sure, but I think the 4 way handshake is required to start the session as well) I don't think the SSID is needed again. So as long as the session remains open you should be good to go.

However as far as I understand there is a timeout. If it gets triggered a new session will have to be established and the authentication and association process has to be repeated. Since you changed the SSID this will fail. Note: Restarting "WLAN restart" on the client or AP will close the session as well, but I think that's obvious.

Some further reading material about how APs work can be found here and here.

Addition: The SSID still can get transmitted e.g. within beacon frames (see Tim's answer). But at this point I haven't found any evidence that it does actually get evaluated the authentication and association process. The fact that it doesn't have to be transmitted within the beacon frame (it can be 0, see here and here) leads me to believe that it does not get evaluated after the authentication and association process. But Superuser is not the right site to ask/answer this type of question anyway.