How do you get to undernet 7 in mega man battle network 3 blue

You must have defeated FlamMan V2 to deactivate his security cube. He is located in a dead-end in Undernet 5. With that out of the way, go to Undernet 6 and make your way as far up as possible and as far left as possible. Through trial and error you'll reach a path leading away to the left and up. If you hit the security cube, you'll know you're in the right place. Continue on, and you'll enter Undernet 7. Huzzah.