Other than these, every team knows which pot group they are in.
Benfica, champions in 1961 and 1962 and runners-up on five occasions, beat PAOK Salonika of Greece 4-1 away after a 1-1 home draw.
Premier League champions City, eliminated by Liverpool in the quarter-finals last term, are in pot one along with defending champions Real Madrid, Europa League winners Atletico Madrid, Barcelona, Bayern Munich, Juventus, Paris Saint-Germain and Lokomotiv Moscow.
Liverpool, Valencia, Viktoria Plzeň, Ajax, AEK Athens and Young Boys's pot will be announced once the remaining play-off places are determined.
Red Star, who won the European Cup in 1991, came back from two goals down in an electrifying second leg in Austria to draw 2-2 and go through on away goals. On towards Real Madrid's chances.
It takes place on Thursday, Aug. 30 in Monaco. And Dortmund should have no problems beating Swiss club Young Boys either.
Juventus is also top-seeded, with new signing Cristiano Ronaldo seeking a fourth straight Champions League trophy to end the Italian giant's 23-year wait for a third European title.
Liverpool are facing a touch task as they - along with Tottenham, Manchester United and Manchester City - prepare for this evening's Champions League group stage draw. And Dortmund will be desperately hoping to avoid them this time around. Had Benfica failed to qualify, Liverpool would have moved up to Pot 2. While Inter Milan are arguably the worst possible opponent in pot four, having made some impressive signings in the summer.