After the Mission Priority: Geth Dreadnought, Legion or Geth VI providing Legion didn’t survive Mass Effect 2, will inform you of the Geth servers in the debrief. This Mission must be completed before doing the Mission Priority: Rannoch, and can be accessed by selecting the Geth Comm Hub.
Choice: Completing the Mission or Not
This mission is worth completing due to rewarding you with the Geth Prime Platoon to your War Assets as well as 12,500 credits. Also, completing this Mission is integral to the Mission Priority: Rannoch, depending on your previous choices.
Complete the Mission
Completing this Mission is the only way to get a peaceful resolution between the Quarians and the Geth. But this requires at least 80% of your reputation bar filled, and both Tali and Legion to be alive. By having those requirements fulfilled, completing this Mission will give you the choice to Rally/Warn the Fleet in the Mission Priority: Rannoch.
Don’t complete the Mission
If you choose not to complete this Mission, you’ll lose out on the credits, and the Geth Prime Platoon War Assets, but more importantly, you’ll lose the choice to end the Quarian/Geth storyline peacefully in the Mission Priority: Rannoch, which’ll end with you eliminating one of the races.