I have 4 routers, two in the middle, R3 and R4, which are just transport, R1 and R4 are the endpoints. I want them to form a bgp relationship then use the GRE tunnel to actually move traffic. The configuration I have is tested and working from a colleague. The problem is that in my home lab I cannot form a BGP neighborship between the two endpoints over the loopback interfaces. I am rather new to BGP, and have only used loopbacks a few times. I can ping the loopbacks on each end from the other end sourced from the local loopback. I have attached the 4 router configs, which are short. Thank you.