i have two network, a wifi and a cable lan.
I want use together, but I want to force iOS Simulator to use only WiFi, because, lan is under proxy, protected, with a lot of limitations, etc, ect...
The iOS Simulator does not get its own internet connection, it uses the computer's. Therefore, if you want it to use the Wifi network instead of the LAN, just make sure you're connected through Wifi.
In System Preferences / Network you can rearrange the order in which the computer gains Internet connection. Just place Wi-Fi on top of the list. On Lion it's done by clicking the gear thingy, and select Set Service Order from the pop-up list.