I am considering reclassing from Infantry to MP. What’s the process to go from National Guard to active duty Army for MP?

Should not exclude you from AIT. Too much of the AIT training is geared toward the support on modern day battlefield which has little to do with civilian law enforcement. When you are in the thick of the fight is not the time to realize you don't know the proper way to read a topo map, call for fire or request CAS. I was a cop who went AD as an MP needed Basic and AIT to figure out the tactical aspect as well as the difference between rules of engagement and laws of arrest. Had numerous deployments in field environmenst. Store bought road maps don't tell ya if the route recon you are conducting can support an armor advance over existing bridges.

You should go see a recruiter but I have a question for you why 11 Bravo? I would be asking the same question about 88 Mike, 92 Golf, or 14 Romeo/ Tango. You most likely would be joining the Army as a Specialist who might need lots of brushing up on your infantry tactics it hypothetically if you do get as infantry you might be going into a platoon who is on a cycle that has nothing to do with Infantry of which you could easily do as an 88 Mike or a 92 Golf. I'm not trying to discourage you but you should consider your options with your experience. Did you say something about CID? That is where you should go as it would be a lot more beneficial for you.

You will still go to AIT. You civilian experience will not get you much of anything.

I can tell you that you may have to do an MOS reclass course which I believe is still two weeks long. However, this is the process of the Reserve Army and I am not sure if this is the case for Active Army.