How to connect local wifi w/o internet gateway?

I have a local wifi network without open internet gateway (firewall locks it).

IPad onnects wifi for few seconds and drops connection:

IP address OK, connection established

Then iPad wants to connect to www.apple.com.

Because of closed gateway, blank screen appears with only a Cancel button.

After Cancel, wifi connection is dropped.

How to setup local wifi connection?

How to force iPad not to drop this connection?

(I do not want to open internet gateway but I want access local servers, run Synology applications, etc.)