What is what kind of dog is duke from secret life of pets?

Duke is a large and fluffy mongrel dog in the movie "The Secret Life of Pets." He is described as being sweet, loyal, and lovable, but also somewhat anxious and insecure due to being abandoned as a puppy. Duke has a scruffy appearance with brown and white fur, and floppy ears. He is one of the main characters in the film and forms a close bond with Max, the protagonist. Overall, Duke is depicted as a friendly and endearing pet who just wants to be loved and accepted.