Playoffs H2H - What happens in a tie?

[NeTWorKz]

We have 18 people in our league, so theirs some people that we don't play twice. Last week, one of the matches were at 6-6 tie and I was wondering, if they tie during playoffs what happens?

If you're wondering about the meeting with them during the regular season, it was 6-6 as well. Who advances then?

[JagrBomb]

then it goes by whoever was the higher playoff seed.