The next time Pep Guardiola feels the need to justify his continued presence in Bavaria – and that time will come – he has some useful numbers to roll out. As of Tuesday night, the most pertinent one available to him is 115. That is the number of goals Guardiola's Bayern team have scored so far this season, a number plenty enough to take them in to the last four of the Champions League, the semi-final of the German Cup and to the cusp of successive Bundesliga titles. It's a funny game, football isn't it? People can grow restless, unhappy even, pretty quickly. As Guardiola himself said on the eve of this undressing of porous Porto, people are only happy here if Bayern win the treble. Bayern Munich's Thiago Alcantara jumps highest to head the home side ahead on 14 minutes and set the German giants on their way . Former Barcelona midfielder Thiago races away to celebrate and clenches his fist after giving Bayern Munich the lead on the night . Bayern Munich defender Jerome Boateng scores the second header of the evening to double Bayern's advantage and level the tie at 3-3 . Boateng points to the skies in celebration after the Germany international's goal gave Bayern the initiative as they led on away goals . Robert Lewandowski made it a hat-trick of Bayern headers on 27 minutes as the Poland striker powerfully nodded the ball into the net . Thomas Muller shoots and scores to give Bayern an incredible 4-0 lead with 10 minutes of the first half still remaining . Muller lets out a roar in celebration and is congratulated by fellow goalscorer Thiago as the Bavarians took full control of Tuesday's tie . Lewandowski powerfully strikes from inside the area to give Bayern Munich a 5-0 lead at half-time as the frontman netted his second . Lewandowski slides on his knees in front of the Allianz Arena crowd after scoring his second goal of the night as Bayern raced away . The Bayern Munich frontman is congratulated by Mario Gotze (left), defender Rafinha (centre) and Muller (right) after scoring . Martinez replies for Porto but the goal was just a consolation as the Portuguese giants failed to stage an unlikely comeback in Munich . Bayern Munich midfielder Xabi Alonso bends the ball past the Porto wall to score his side's six goal of the evening with two minutes to go . Alonso jumps in celebration and points to the sky as captain Philipp Lahm races over to congratulate the Spanish midfielder . Bayern Munich (4-3-2-1): Neuer 6, Rafinha 7, (Rode 72, 6) Boateng 7.5, Badstuber 7, Bernat 7, Lahm 7, Alonso 7.5, Thiago 7.5 (Dante 90), Muller 8, Gotze 8 (Weiser 86), Lewandowski 8.5 . Subs not used: Reina, Schweinsteiger, Pizarro, Gaudino. Booked: Badstuber . Manager: Pep Guardiola, 9 . Scorers: Thiago 14, Boateng 22, Lewnadowski 27, 40, Muller 36, Alonso 88. Porto (4-3-3): Fabiano 4, Reyes 4 (Ricardo 33, 6), Maicon 5, Marcano 4.5, Martins Indi 5, Herrera 5, Casemiro 4.5, Torres 5, Quaresma 5 (Neves 46, 6), Martinez 5, Brahimi 5 (Evandro 67, 6) Subs not used: Helton, Quintero,  Hernani, Aboubakar . Scorer: Martinez, 73. Booked: Ricardo, Marcano, Herrera, Martinez. Sent off: Marcano . Manager: Julen Lopetegui, 5 . Man of the match: Robert Lewandowski . Referee: Martin Atkinson (England) 8 . Attendance: 70,000 . Well, despite the horrors of the 3-1 first leg defeat in Portugal last week, that remains very much on and the statistics show that Guardiola and his players have indulged in a fair amount of self-expression along the way. Guardiola won't remember all the season's goals. He won't remember all of the seven Bayern scored against Roma and against Shakhtar, the eight they plundered at home to Hamburg or the six they put past SC Paderborn. The Spaniard will remember the half dozen his team scored here on Tuesday night, though. He will remember them - especially the five that came in a brutal, spellbinding opening half - because they will be set against the background of last week's defeat and the disgruntlement that followed. Questions were asked about his own future, Bayern's club doctor walked out, slamming the door behind him. By half-time, though, those matters seemed rather distant already and that is what brilliant football does. It makes people forget the small details. That, in a way, is the whole point of sport. Certain Bayern's rather entitled supporters will have seen little better than this over the years. Not just because of the quality of the football but because of the context and because of the sheer hunger and monotonous forward drive of this team. 'I knew my players could do this,' said Guardiola afterwards. 'But this was not perfect. We can still improve.' Having started so badly in the first leg last week – Bayern were two down early– they needed to reverse things quickly. After 23 minutes they were two goals up and, from that point on, the contest was no longer valid. Lewandowski had already struck the post when Bayern took the lead, left-back Juan Bernat crossing to the near post for Thiago Alcantara to thump in a header. The goal served to break the tension a little and as Porto failed to settle, Bayern began a hypnotic and relentless journey through the gears. A shot from Thomas Muller was saved by Fabiano soon after but that proved a rare moment of competence for the Porto goalkeeper. He had a poor night and was beaten for the second time midway through the half when Jerome Boateng glanced a header in by the post after a corner. At this point, Bayern were already mathematically through. Porto needed to score to maintain an interest but they were too skittish, too panicked and too intent in arguing with referee Martin Atkinson to ever get a foothold in a game that quickly galloped away from them. Bayern Munich celebrate in front of their delighted fans after overturning a first leg deficit to reach the Champions League semi-finals . Muller celebrates with supporters at the full-time whistle while Porto defender Maicon looks dejected as Porto surrendered a first leg lead . Porto's Algerian frontman Yacine Brahimi looks to control the ball in the air under pressure from Bayern Munich right back Rafinha . Ricardo Quaresma, who scored twice in Porto's first leg victory, attempts to get the better of Bayern's Spanish left back Juan Bernat . Porto defender Diego Reyes slides in to a challenge to dispossess Bayern Munich frontman Mario Gotze during the first half . Colombia international Jackson Martinez, who scored Porto's third goal in the first leg, controls and shields the ball from Rafinha . The third goal arrived soon after – Lewandowski finishing first time after Philipp Lahm had set him up beautifully – and it was at this point a massacre seemed in the offing. A drive from Muller from distance then struck defender Casemiro and span through Fabiano's flapping legs in the 36th minute and, after a rare Porto attack culminated in a dive by, and a booking for, Jackson Martinez, Lewandowski struck again, teasing two defenders before arrowing a perfect shot in to the corner with his right foot. Half-time found the Portuguese on their knees and they crawled to the dressing room. Beyond that, Bayern lost some momentum and Porto even scored a goal, Martinez heading in. On the touchline, however, Guardiola's greatest inconvenience was a split to the seam of his suit trousers. As time wore on, he continued to instruct his players feverishly. At times he must be exhausting to play for. In the stands here, meanwhile, Manchester City's football director Txiki Begiristain looked on covetously as Xabi Alonso curled in a free-kick at the death after the dismissal of Ivan Marcano. City, as we know, could do with a man like Pep. They are not alone. Porto duo Oliver Torres (left) and  Martinez (right) look dejected as Bayern Munich stormed into a 5-0 lead at half time . Bayern Munich manager Pep Guardiola holds his head in his hands after a missed chance having ripped his trousers in celebration . Guardiola gives captain  Lahm instructions on the touchline as Gotze, Thiago and Muller take a breather during a break in play . Porto manager Julen Lopetegui and Bayern Munich boss Guardiola - former Barcelona team-mates - share a joke ahead of the game . Gotze (on the left of the middle row) posted this picture of the Bayern Munich celebrations on Instagram . Injured trio Franck Ribery, Mehdi Benatia and David Alaba chat in the home team dugout ahead of Bayern's quarter-final tie . Holland international Arjen Robben, who was also sidelined through injury, was a pundit alongside Oliver Kahn (right) on Tuesday evening .
Bayern 5-0 up at half-time as Robert Lewandowski (2), Thomas Muller, Thiago Alcantara and Jerome Boateng scored .
Former Liverpool and Real Madrid midfielder Xabi Alonso scored Bayern's sixth in the closing stages .
Porto had gone in to the match with a 3-1 lead from last week's first leg in Portugal .
Colombia international Jackson Martinez scored a consolation for Porto with seventeen minutes to go .
Porto's Spanish defender Ivan Marcano was dismissed in the 86th minute after picking up two bookings .