[SOLVED] Strange 2.4Ghz band authentication issue.

[Darth Sicaedus]

TL;DR: Brand new Owlet baby monitors could not authenticate on the 2.4Ghz band until I switched it from 802.11 b/g/n support to 802.11 b/g support.


Today at work, I was working with a daycare to get these Owlet SIDS prevention, baby monitors connected to the wireless. This daycare is located in an elementary school that my company does IT support for. The daycare and school district have a weird sort of symbiotic relationship with each other since the enrollment has been low. They needed a way to subsidize the funding they weren't getting from state or federal, allowing them to keep that building open. Anyway, the school has HP MSM410s and a handful of MSM430s wireless access points and an HP controller. I spent the better part of my day trying to figure out why I was getting authentication errors from the baby monitors saying that the PSK was wrong. I talked to Owlet's support who basically said that these were designed with residential style networks in mind and didn't really give me much to go on. I found one of their KB articles while talking to the support guy, stating that the monitors were designed to connect to 802.11 b/g networks. That gave me the idea to change how the localized APs were broadcasting the 2.4Ghz band to 802.11 b/g instead of b/g/n. Once the APs had sync'd the change, I was able to connect the monitors just fine.


Has anyone else run into anything like that before? I know my controller and APs aren't on the latest firmware, but they were updated August 2018 to what was the latest at the time. I strongly doubt updating them would have solved that issue.

 

[Solandri]

Most b/g/n devices can only operate in one of those modes, not multiple modes simultaneously. They only have one 2.4 GHz radio, and have to interpret the signals it receives based on the 802.11n, g, or b standard. Using one precludes the other two (unless you've got multiple 2.4 GHz radios). Since n is newer, most modern 2.4 GHz routers default to using 802.11n. If your baby monitors don't support n, this would effectively lock them out of the network. If no n devices are using the network, then the WiFi router could fall back to b/g mode. But I'm guessing since n is preferred, the presence of a single n device prevents the use of b/g mode.

The converse consequence of this is that if you switch the network to b/g to force it to work with the baby monitors, then all 2.4 GHz devices using the network will fall back to b/g. This is generally not a good thing. Not only are b/g slower than n, but they don't support per-device speeds. With a n router, it can communicate with each device at the fastest speed that device is capable of (giving the signal strength and quality). b and g networks will downgrade the entire network to the speed of the slowest device that's connected. So if someone way off in the corner of the building connects to your b/g network and is only able to manage 1 Mbps, every device's speed will slow down to 1 Mbps.

So if your budget allows, I would recommend setting up a separate 2.4 GHz b/g network just for the baby monitors (taking care to make sure their channels don't overlap the primary 2.4 GHz network's channels). Or to upgrade your baby monitors to ones which work on 2.4 GHz n or 5 GHz ac networks.

 

[Darth Sicaedus]

Thanks for the information. They will be upgrading the wireless over the summer to dual band AC or possibly AX APs. Everything they have for client devices is 5Ghz compatible and that wing is where all the dual band MSM430s are in the building.