I searched high and low unsuccessfully for instructions on how to set the link speed and/or duplex on one of the ports of an ASUS router (in my case, the RT-N66U, though I think other ASUS router...
https://blog.kamens.us/2014/11/30/howto-set-the-link-speed-duplex-of-a-port-on-an-asus-router/
I’ve just encountered a new (at least for me) scam in the ongoing quest by retailers and manufacturers to make rebates more and more onerous to apply for and therefore less likely to cost them ...
https://blog.kamens.us/2009/12/20/new-scam-pay-a-usurious-fee-to-get-your-rebate-faster/