With last firmware ( tried RUT2XX_R_00.01.06.1 and also RUT2XX_R_00.01.10 ) I've noticed a very slow speed on configuration pages.
I've noticed it using Chrome browser with local access and with remote access (Dynamic DNS). I use HTTPS for remote access.
Once I did the login using Firefox instead of Chrome. With Firefox the speed is good.
Just to let you know about this issue and hope will find the solution for next firmware.
