Issues Flashing Netgear R7800

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kosist
DD-WRT Novice


Joined: 30 Mar 2021
Posts: 3

PostPosted: Tue Mar 30, 2021 9:11    Post subject: Issues Flashing Netgear R7800 Reply with quote
Router: Netgear Nighthawk, R7800.

Let me please ask for the help.

I've flashed 20 routers, and just for 16 of them it was possible to reflash with ddwrt image.
I've followed manual which I've found on this website. Also, tried different ddwrt builds for those routers which are failing - but it didn't help.
Actually, after flashing router constantly reboots. Reset does not help. So I have to use Tftpd64 application in order to reflash it with origin Netgear firmware.

I've tried also to clear nvram via telnet - but it didn't help.
Could anyone give me some hint of how to troubleshoot the issue? Because strange is that for 16 routers everything was fine - just 4 others (same model, same initial firmware from NetGear, all routers are "fresh", just purchased new routers) do not "want" to be flashed with ddwrt...

Thanks a lot in advance,

Sincerely, Ivan.
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blkt
DD-WRT Guru


Joined: 20 Jan 2019
Posts: 5660

PostPosted: Tue Mar 30, 2021 9:40    Post subject: Reply with quote
This is likely due to defects in the NAND flash, or bad blocks, assuming same hardware revision.
kosist
DD-WRT Novice


Joined: 30 Mar 2021
Posts: 3

PostPosted: Tue Mar 30, 2021 10:15    Post subject: Reply with quote
Thanks a lot for the replies!
Actually, I've tried build 44715 from here https://dd-wrt.com/support/router-database/?model=R7800_v1 (which works on others 16 routers), and also I've tried Kong's build recommended in the manual, v40720.
I've checked NAND via telnet and nanddump, and seems that 3 nands have bad blocks.
Hope that this will be enough to be able to return routers to the supplier - because I guess uploading of "not native" firmware ddwrt issue is not a reason for complaint... But bad NAND could be.
blkt
DD-WRT Guru


Joined: 20 Jan 2019
Posts: 5660

PostPosted: Tue Mar 30, 2021 10:27    Post subject: Reply with quote
kosist wrote:
I've checked NAND via telnet and nanddump, and seems that 3 nands have bad blocks.
Hope that this will be enough to be able to return routers to the supplier - because I guess uploading of "not native" firmware ddwrt issue is not a reason for complaint... But bad NAND could be.

I would avoid mentioning DD-WRT, instead only if they insist on more information you can say from Telnet.

Enabling Telnet is possible with older version Netgear factory stock firmwares.
kosist
DD-WRT Novice


Joined: 30 Mar 2021
Posts: 3

PostPosted: Tue Mar 30, 2021 11:12    Post subject: Reply with quote
blkt wrote:

I would avoid mentioning DD-WRT, instead only if they insist on more information you can say from Telnet.

Enabling Telnet is possible with older version Netgear factory stock firmwares.


Yes, sure, thank you - I'll not mention about DD-WRT, because then it is for sure not the warranty issue.
ho1Aetoo
DD-WRT Guru


Joined: 19 Feb 2019
Posts: 2927
Location: Germany

PostPosted: Tue Mar 30, 2021 11:25    Post subject: Reply with quote
well badblocks are normal, pretty much every NAND chip gets badblocks over time
this is normal cell wearout

It becomes problematic when the badblocks are located in certain areas

one could argue at most that a new chip should have no badblocks, these are then B-Dies...

is also the question whether you have to be satisfied as a customer with B-goods

but I can tell you what the manufacturer will say "badblocks are normal, every NAND chip has them"

i am always glad that we in europe have a 14 day right of withdrawal for online purchases
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