There is a D-Link DIR-825 Rev.D1 router .
On habr, I saw an article about filtering traffic through a router and wanted to do something similar, but was disappointed that only stock firmware is supported.
There is also a Cubietruck plugged in via LAN .
Is it possible to filter through it?
if the device is equipped with at least two network interfaces ( ethernet , wifi , bluetooth , etc.), then – yes, you can filter the traffic passing through the device between two network interfaces.
if there is only one network interface, then, theoretically, it is possible, but, firstly, the configuration becomes much more complicated, and secondly, such use carries, as it seems to me, very little sense.