I want to expose some APIs in Bluemix from my datacenter using API Connect and the Secure Gateway, but I need that just API Connect can call this APIs because I am going to secure them with this service. I have been trying to do this with the IP tables configuration of the Secure Gateway Destinantion, but I do not know the IP address that makes the calls to the other APIs, is there any way to do this?
You are looking for the IPs of the API Gateway that actually handles each API call. However, this is not a good mechanism for access control, as those IPs may change at any time.
Instead, why not enable Mutual TLS on your destination, then just upload the cert and key to a TLS profile within API Connect? Applying that profile to your policy assembly will effectively limit access to the Secure Gateway.