I have never used dd-wrt let alone installed it on a device but would like to start. I have an Asus RT-AC56U and have read it has dd-wrt support. I have looked around and cannot find installation instructions for this specific device. Not sure if I have just overlooked it but I would appreciate some help finding installation instructions.
Looks like this guy in the second post just flashed it from the web gui. http://www.dd-wrt.com/phpBB2/viewtopic.php?p=764491
That's the way I've always done it on my RT-N16.
The firmware he links there is old though. Here's the newest one... ftp://ftp.dd-wrt.com/others/eko/BrainSlayer-V24-preSP2/2014/12-22-2014-r25697/asus-rt-ac56u/
I haven't had much luck the last year or two with DD-WRT. Seems like there's always at least one thing I need that's broken. A couple months ago it was the VLANs. No changes in the GUI or telnet/SSH would take effect. So I went back to Tomato and now wish I would of switched sooner. If you're interested, Shibby makes some good builds... Download - http://tomato.groov.pl/download/K26ARM/124/