Hmmm, that depends on your six month old! My daughter had 2 naps a day until she was almost 18 months. One shortly after breakfast and one about 3 pm. Each lasted about and hour and a half. My son on the other hand who is 6 months now takes a long nap (about 2 1/2 hours) after lunch and sleeps well through the night.
Sounds to me though like you may be going through teething problems with your baby. My daughter would not sleep at all when she was teething. She was not unhappy, just uncomfortable. We gave her Tylenol and teething tablets which helped some, but she still woke up at night. Tylenol really only works for about 4 hours. You might give it a couple of weeks and see if the teething lets up or see if switching her to 1 nap a day and an earlier bed time might help.