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I've recently taken a on a new broadband service with Vodafone superfast 2 package with the latest Vodafone router.
Within the GUI you're able to split the SSID's so you can have unique SSID's for both the 2.4 and 5GHz channels, great!
However once you split these SSID's the router disables the 5GHz connection, I've tried various different ways of working with this and none seem to work.
I work in this exact industry and use routers and switches on a daily basis as part of my job, there seems to be a bug within this firmware version.
Firmware version is 19.2.0203-3261005-20191217122049-2861ba0dea80e3c1bd5a2e7c5fb0527a1550a0a2
Vodafone, this router is not performing as it should, please report back with a new updated firmware.
If you are in "the industry" then you've not discovered the half of it yet! My advice would be to just get your own modem+router.
Currently, there seem to issues with local subnet routing - you can't hook up a switch to one of the router ethernet ports and rely on it to route properly (so no local DNS servers, no reliable DLNA, and file sharing is iffy). In addition to the SSID issue, if you change the available IP ranges some combinations cause malfunctions.
*Rather than splitting the SSIDs you used to be able to filter the different bands by MAC addresses - in many situations a much more elegant solution for the average user attached to your network.