Docker0 bridge, IP address and slow speed for transmission


I’am quite new to linux and Rockstor(nice NAS Distro) and have some questions about the docker0 bridge.
My lan is set up as a 192.168.x.x network, but the default docker0 ip address is172.17.0.1/16 ->do I need to change this? I tried to change it once before and it broke my Rockstor installation. I allthough se a very low download speed in transmission, ~400kb/s vs 4-5Mb/s on a Windows machine with the same torrent. Is this normal?