After the rearranged round 10 games last weekend, Ulster moved up to fourth at the expense of the Cardiff Blues who still have a game in hand over the Irish province.
Both teams are in action on Friday night, with Ulster travelling to Glasgow in the hope of improving their away record in Scotland where they have won just once in their last four trips.
The Blues, meanwhile, welcome table-topping Munster to Cardiff. Despite there being a 14-point gap between the teams in the table, Cardiff must take heart from the fact Munster have not defeated them on home soil since 2005.
The second-placed Ospreys, the only non-Irish side in the top-four, are in action on Saturday night in Edinburgh.
If the Welsh region are to continue their push for a home semi-final they will need to take points from this game, any slip-up could see another Irish province, either Leinster or Ulster, move into the coveted home play-off spot along with Munster.
The other Saturday game sees eighth-placed Connacht travel to Italy to face Aironi, who are still looking for their elusive first Magners League victory.
Connacht, however, will be keen to maintain their push for a highest ever finish in the Magners League.
The round wraps up with two games in Wales on Sunday. the Newport Gwent Dragons hosting third-placed Leinster and they Scarlets facing Benetton Treviso.
The results from both matches could be crucial for the Welsh regions' hopes of qualifying for the Heineken Cup next season.
The Scarlets currently sit in sixth place in the table, having slipped from second over the past few rounds, with the Dragons just one place below them in seventh and with a game in hand.
Looking closer to home, the Scarlets need the victory to maintain their chance of a top-four Magners League finish.
MAGNERS LEAGUE - ROUND 18 FIXTURES:
Friday, March 25 -
Cardiff Blues v MUNSTER, Cardiff City Stadium, 7.05pm (live TG4/BBC 2 Wales)
Glasgow Warriors v ULSTER, Firhill Stadium, 8.05pm (live BBC 2 Northern Ireland/BBC ALBA)
Saturday, March 26 -
Aironi Rugby v CONNACHT, Stadio Zaffanella, 5.30pm local time/4.30pm Irish time
Edinburgh v Ospreys, Murrayfield, 6.30pm (live S4C/BBC ALBA)
Sunday, March 27 -
Newport Gwent Dragons v LEINSTER, Rodney Parade, 2.30pm (live RTE 2/S4C)
Scarlets v Benetton Treviso, Parc y Scarlets, 5.35pm (live BBC 2 Wales)