Hi I have a 3 year old hound mix dog. He has been shaking his ear and scratching it. Also externally the ear is very red. What is this and what can I do for him. I regularly clean his ears with ear cleaning fluid for dogs so I don't think that it is from dirt.

If you have already tried cleaning his ears and seen no improvement then I would say he either has mites or an infection both of which need to be seen to by a vet for treatment.

You will most likely be given ear drops to administer.
To do this you simply hold the dogs ear over its head and put required amount of drops in (depending on the size of your dog you may need some help)
Then put his ear back down and rub the outside, this will help push the drops further down the canal.

Sounds like an ear infection. Possibly yeast.
Get him to a vet, they will do an ear swab to see what it is and administer the proper meds to remedy the problem.

If his ear has a bad smell or dark brown waxy stuff its either mites or yeast infection, which regular cleaning will not clear up, its need to be treated with medicated ear drops from the vet. If there is no smell or dark wax then it may be a bug or part of the cotton or what ever you clean the dogs ears with. Either way take to trip to the vet.

Take him to the vet.

This is probably driving him crazy.

My dog had ear mites one time like Shaz mentioned, and he scratched himself raw.

They scratch at it, but can't really get to where it itches, on the INSIDE.

Whatever his problem, take him to the doctor, and end his misery.

With my GSD it was an allergic reaction - her one ear becomes inflamed, sore, she spends most of her time trying to insert her foot into her ear canal, long before she develops the redness under her legs, on her belly.