We have several several-year-old XS708Ev2 switches that have just been retired from one use and will soon be given another. This seems like a good time to update their firmware; they all came with V1.0.0.15, and according to support.netgear.com the latest version is V1.6.0.30.
I downloaded https://www.downloads.netgear.com/files/GDC/XS708Ev2/XS708Ev2_V1.6.0.30.zip and unpacked the .zip file, yielding two files: release notes in HTML and XS708Ev2_V1.6.0.30.flash. Using the web-management interface on the switch, I went to Maintenance -> Firmware Upgrade, browsed to and selected the .flash file, and clicked Apply. The switch began to load the file, then stopped with the complaint
Invalid firmware image! Please double check!
What's going on? Is this not really the right firmware upgrade, and if so, where's the good stuff? Is the old firmware so old that it doesn't recognize the new (1.6 does sound a lot newer than 1.0)? Does upgrading through the web interface just not work for some reason?
The answer turns out to be simpler and even more annoying than I'd expected: the XS708E's web management can't upload firmware through current versions of Firefox.
Background I should have supplied with the original query but didn't: I'm managing the switch through its web interface, using Firefox 93.0 (the latest version) running on Ubuntu 18.04 Linux.
On one hand (and with thanks to @schumaku for the pointer) I tried loading various back editions of firmware, back to 1.0.0.15, the version already running in the switch. All encountered the same `Invalid firmware image' error.
On the other, I tried unpacking the 1.6.0.30 .zip file on a much-older Linux system I have running at home, and using the tools built into a current Android tablet. The resulting .flash file was identical in all cases.
So it seemed improbable that it was an unpacking error, both because different versions of unzip produced the same result, and because the same error happened with several different versions. (Also because I've upgraded firmware in other Netgear switch models both far in the past and a few weeks ago and all was well.)
So finally it occurred to me to try a different browser, and I fired up the version of Chromium available as an Ubuntu package, and 1.6.0.30 installed just fine!
Apparently something about the Javascript the switch sends to the browser doesn't work as expected under at least current versions of Firefox, and either the data are scrambled or the header check gets it wrong. But the relevant code inside Chromium is different and all is well there.
The same bug obtains when the switch is running 1.6.0.30; if I try to upload the firmware again when the new stuff is running, it still errs if I use Firefox, and still succeeds if I use Chromium. So it would make sense for Netgear to treat it as a real problem and try to mend it for a future release. (I'll be happy to help test such a fix; we don't plan to put all our XS708Es into production, we always set aside a few spares.)
But for now I can upgrade our switches to the current standard and that's all it takes to make me happy.
