The guide on portforward.com does not have your specific router but suggests that including port 27965 is needed (I have no idea why) and that NAT must be enabled too.
This is the original ioquake3 code :
#ifndef STANDALONE
#ifndef AUTHORIZE_SERVER_NAME
#define AUTHORIZE_SERVER_NAME "authorize.quake3arena.com"
#endif
#ifndef PORT_AUTHORIZE
#define PORT_AUTHORIZE 27952
#endif
#endif
#define PORT_MASTER 27950
#define PORT_UPDATE 27951
#define PORT_SERVER 27960
So it seems logic to me forwarding ports 27952 , 27950, 27951, 27960 for q3 1.3x ... but since OA doesn't need authorization and doesn't receive internet updates notification ( ports 27952 and 27951 ) , it should have sense forwarding only ports 27950 and 27960.
Maybe that was different for one or some older versions of q3.