If you receive a complaint and do not answer the complaint within the alloted period of time (generally 28 days), you are essentially admitting that everything in the complaint is true.
When there is no genuine issue of material fact shown, then a judgment is granted on the claim submitted. In other words, the other side automatically wins. A judgment is issued in their favor. There is no discovery, no nothing - you lose.
So you DO NOT want to ignore the complaint. You WANT to answer the complaint WITHIN THE TIME PERIOD SPECIFIED ON THE COMPLAINT, and admit, deny, or say that you do not have sufficient knowledge to either admit or deny the claims made.
Then you want to file an affirmative defense.