Hello
Perhaps there are multiple network adapter/ NAT in between, you should check what IP is resolved for ECC in BW system and your BW system should can connect to it or you should adjust your DNS to let BW use the correct IP to connection.
If you are using NAT, please refer the following wiki
RFC connections on “NATed” environments - ABAP Connectivity - SCN Wiki
Best Regards,
Yong Luo