I can't understand your question, as if the upload is corrupted the firmware doesn't install and/or you can have generaly a bricked router.

When I upgrade my Tomato Toastman, at the end of the upload I have a message that upload was successful.. That's enough for me.

You can't upload the file, verify the checksum then install it if that was your background idea.

WNR3500L running Toastman's Tomato.

Dennison said: Striatum. Netgear has told me there is no way to ensure that if any firmware is installed other than Netgear, they cannot guarantee that the factory recovery disk firmware will 100 percent over write any remnants that another 3rd party firmware left behind.

1- It is exactly the same with computers: even if you reformat, you don't erase disk sectors, and you have remnants that can be recovered by specialized softwares... So I can't see what is specific to routers in your question.... All the computers we use are full of ghosts on the disks and they run well !!!

If you want to restore Netgear firmware you just have to erase NVRAM before reverting (it comes back to defaults settings)  and there will be no risk of collision between the firmwares. The problem is well known even when upgrading between tho version of the same firmware you sometimes have to erase NVRAM to avoid bugs.

2- There is only one method to be sure that a firmware is installed 100% correctly: it works !!!!!!! I repeat, if the installation is not 100% succesfull, either the firmware is not upgraded (most of the cases) or if you really have no chance the router is bricked.

How do you know that a software is 100% installed ????? It works... What I can't understand is why you are concerned by this problem for router and not for a software, or an OS that you reinstall... It is exactly the same. 

And yes if the upload is complete it means that files have been checked and that files have been correctly copied to their destination folders... Upload means 'installation' in that case...So upload = success means installation = success.... If there is a flaw during any part of the process you won't have the success message.

And believe me, I use alternative firmwares since one year, and I can't imagine reverting to stock Netgear software... You should perhaps ask yourself if you really need to burn an opensource firmware, if you are wondering about this sort of problem.

WNR3500L running Toastman's Tomato.

Exactly if you erase NVRAM (all alternative firmwares have this function implemented in GUI) before flashing any firmware there will be no conflict.

Open source firmwares don't install anything like a bootloader. They only replace the OS, for example it is as if you have a computer running Ubuntu GNU/linux and you replace it by Fedora GNU/Linux. The NVRAM can be compared to the 'home' separate partition that you are supposed to have in Linux, and that is preserved if you don't erase it manually before changing your Linux OS. If Fedora and Ubuntu don't have the same way to save your preferences in 'home' there could be problems... (in fact there is no problem, but it could lol).

WNR3500L running Toastman's Tomato.

Tomato has a GIT resource to compile it by yourself if you want... I've tried and managed to compile Tomato from Git but some very skilled people, like Toastman or Kong make very very well .... Tomato is not strictly opensource, see:

- http://tomatousb.org/tut:how-to-build-and-rebuild-tomato-for-total-noobs
- http://tomatousb.org/forum/t-309276/ (for licensing)

DD-WRT I don't know if source code is easy to obtain.

Erase linux is not the appropriate command I think, it erases all the firmware I think... You take the risk to brick your router.

You know sources are probably many thousand lines long, plus all patches and bug correction.... so help yourself if you have the courage....

WNR3500L running Toastman's Tomato.