Upgrade failed with 21061, 21286, 21676, 22118.
I found that my NetGear WNR2000v3's CPU is AR7241 rev 1.1, but DD-WRT's webpage said it's AR7240.
Maybe my WNR2000v3 is different from DD-WRT programmer's so that could be the reason which made the later firmwares incompatible to my router.
Thanks. But after applying the code in Cron, my wired LAN connection become unstable in 2 minutes.....
After cleared the code, the problem disappeared.
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I cleared all the commands and crons, retyped v3.3 script and executed it (instead of saving it startup), then left it unedited.
And now the automatic MAC changing seems to be working properly. The green LED blinked 4 times when I was replying here. Ifconfig also shows the MAC has been successfully changed.