Download the new RouterOS 5.21 release over the torrent network: http://www.mikrotik.com/download/routeros-ALL-5.21.torrent
Otherwise please visit http://www.mikrotik.com/download to pick exact version!
5.21 changelog:
*) route - fix dst-prefix filtering did not return routes when routes with different routing-mark were present;
*) wireless - improved nv2 stability;
*) winbox & webfig - added simple new version downloading & upgrading panel;
*) dhcp server - immediately store to disk changes for lease configuration;
*) lcd - improve graphs screen
*) lcd - improve touch screen (must /lcd reset-calibration)
*) smb - fix smb share mounting on linux systems
*) ovpn - fixed memory leak on disconnects;
*) userman - fix unpaid profile activation while authenticating;
*) sstp - fix high CPU usage on SSL handshake;
*) winbox - added ability to add time & date to dashboard;
*) metarouter - fixed lockups on RB110AH;
*) metarouter - fixed occasional lockups on RB450G;
*) ups - fixed problem connecting to USB device, introduced in 5.20;
*) quickset - added Wireless PTP Bridge mode;
*) fix MPLS MTU configuration usage;
*) dns - fix empty response;