I explain subnetting in depth here in a now legacy course:
Also with multiple episodes to follow up on it. Please begin with the episode I linked here. If you have additional questions, please feel free to post here. Your question will not only help you but also others in our membership that may have the same questions. I or someone on our team will be able to help answer them here!
*if the post above has answered the question, please mark the topic as solved.
**All "answers" and responses are offered "as is" and my opinion. There is no implied support or guarantee by the ITProTV team.