Standard in the firmware dd-wrt is a function of changes in link speed (10/100 mb/s) that shit is not working!
Because with this had to search a suitable solution is found:
The only utility audit port for dir-320, which fully works. It is possible to disable / enable the ports individually, translate the port in different modes (none | disable | block | listen | learn | forward), tagging, and velocity of the interface. Similar utilities such as ethtool and mII-tooles fail (stupidly did not work).
./robocfg port 3 media 10FD
thats make port 3 to 10 mbs. how its so easy. I'm using it because my cabble in not good.