I've got an issue that I'm not understanding. I've attached a diagram. The topology represents something that I need to do in production.
RTRA advertises a route to the ISP and TransAS. TransAS then advertises this route to RTRB, which in turn will readvertise to the ISP. The ISP shows both routes in its BGP table.
RTRB prefers the route through the TransAS instead of the ISP, which isn't what I want. I created a route map on TransAS that would prepend its AS for any routes that come through it because I always want the ISP to be preferred.
Once I applied this route map to the neighbors on TransAS, the routes still get advertised to RTRB, but RTRB now no longer advertises to the ISP. I can shut down RTRA's interface to the ISP and RTRB will advertise the network out.
Why will RTRB not advertise the network until RTRA goes away? Is this the correct way to do this, or should I just consider running OSPF or EIGRP over this link with the "TransAS?"