Boxer Mix Dogs I Have Two Male Dogs- A Boxer And A Lab Mix, They're Fighting...?

I have two male dogs- a boxer and a lab mix, they're fighting...? - boxer mix dogs

I have two dogs, a boxer and a lab mix too. The boxer is 2 years old and is neutered. The laboratory was not neutured and it is one years. Recently, they began to fight each time they are together. So far (this year), I never had problems with sympathy. At the moment I put them to consider. Who knows how I can stop the fight?