My dog is a shelter rescue so I don't know what breed he is. My best guess is a Rhodesian Ridgeback/ Boxer mix. Ridgebacks are relatively rare and so if you are guessing that as a mixed breed it is usually wrong. However, I've had several people with purebreds stop me on the street and note the resemblance in addition to his kind of unusual personality which fits. If he was more vocal, I'd think redbone coonhound/boxer but he is very very quiet.