How can I stop my dog from being agressive?

First off, you should never touch your dog, make eye contact, or act nervous in front of him,. Touching and eye contact only reinforces his aggressive behavior and he can feel your nervousness and it makes him nervous. What you need to do is talk to your new neighbor and see if you can talk them into taking his dog for a walk. You need to walk your dog by the beagle and if he acts up, take him the other way. It will take a while, but it should work. I'm not sure what else to do, so I hope that works! Good luck.