@russellhaering and I talked about it yesterday, each data center have three different ports, one is connected to agent, and the other two are connected to other two data center.
and mapping is if configure=dfw then agent <-> xxx.xxx.dfw-01.xxx.xxx, and xxx.xxx.dfw-02.xxx.xxx <-> xxx.xxx.lon-x.xxx.xxx, xxx.xxx.dfw-03.xxx.xxx <-> xxx.xxx.ord-x.xxx.xxx