You should be able to go directly to the latest release via the gui, but since it's such a big jump I would make sure to do a factory reset following the upgrade, select to do a 'format jffs at next boot', then reboot twice.
Next step then is to reconfigure with your desired settings (don't use a saved configuration).
Got some issues and took some time to resolve them. I'll list them here, maybe it's good to add to installation notes for other people to know.
- The direct upgrade via WebGUI from Merlin 374.41 to v34E3 was successful. Things seemed good: Internet was available, WebGUI access works normally, old settings were retained. However, I did not test more as I proceeded to perform the Factory Defaults right away. That's when issues arose.
- Right when the router came back, it welcomed me with a quite slow QIS WebGUI. Did not know how I luckily clicked past those QIS setup pages, usually had to click 2-3 times, when a page loaded, it usually loaded without images just like when you browsed a slow page and their images were timed out).
- After the QIS Welcome, the WebGUI pages showed all web elements (images, buttons) normally, but were still slow. Clicking every function needed around 15-30s for a page to load.
- Alright, maybe because there was still one thing we hadn't done yet: format JFFS. So I applied the "Format JFFS at next boot", and clicked Reboot.
- The WebGUI was then still slow. Tried some more Factory Defaults, Format JFFS and Reboot. WebGUI was still slow.
- Thought maybe something with the nvram (?!). So I ssh'ed and performed the "mtd-erase -d nvram".
- Alright, the QIS Welcome showed up fast, webGUI worked normally. Thought things were resolved. But no, Internet was not available
(Actually, it was the laptop wired to N66U did not have Internet connection, I did not check on the router itself which I'll mention in later steps).
ISP Modem ========= WAN[Router]LAN ==============Laptop
- Performed the Factory Defaults, and webGUI became slow again, and this time it was worse as the laptop still did not have Internet connection.
- Alright, maybe it was time to perform an upgrade using Restoration Tool or CFE miniWeb. I tried the CFE miniWeb method.
- I *skipped* the QIS Welcome and browsed 192.168.1.1/index.asp directly as I was so fed up with that step in previous tries. Terrible mistake. I saw that the router had Internet connection, on Network tools I could ping websites, but the laptop still did not have. Did not know the reason, I tried another chaos of Factory Defaults, clear nvram using WPS button... and always *skipped* QIS Welcome, so the issue was always there.
- Ok, held my breath, tried everything from start again: CFE miniWeb, QIS Welcome page showed up fast for me to perform inital setup, Factory Defaults, went through QIS Welcome page once again, applied "Format JFFS" right away, reboot, reboot again. Now everything is fine.
In summary, here are my thoughts on the order of the steps to do for a successful upgrade from Merlin 374.41 to 34E3:
- Direct upgrading via webGUI works, but obviously normal Factory Defaults cause issues for the webGUI.
- So, instead of perfoming Factory Defaults after upgrading, you would want to clear nvram via SSH first (maybe better than WPS method?)
- Only after that, QIS Welcome page would show up fast for you to perform initial setup. And do not skip that step.
- Now you can proceed to apply Format JFFS. Click Reboot.
- Finally, perform Factory Defaults. Wait for the router to reboot.
- Go through QIS Welcome again. You're done.
Still curious why QIS Welcome is a must, I have always thought it is just a wizard so we can skip and set things up manually...?