i know that there isn't code inside my question, but i think this is an interesting question...
Is possible to add a new ip ( preferably ipv6 ) on the wifi network card still connected over ipv4? I have to talk at the same time with a router (ipv4) and another device (ipv6). So is possible to develop this over objective-c? so on the iphone?
On iPhone? Not a chance (AFAIK). I could see that introducing all sorts of security vulnerabilities that would seriously impair the entire purpose of sandboxed apps. *
That said, the iPhone is perfectly capable of binding both an IPv4 and IPv6 address, and will do so automatically in various cases (such as when an IPv6 capable router is offering up both, as mine do). You should watch the Advanced Networking (or something to that effect) videos from WWDC 2010 and 2011. But this is handled at the device, not app, level.
On OS X you have the System Configuration framework in the Core OS layer of the system stack. I think you can use it to set IPs, but I've never really looked into it, and the iOS System Configuration APIs appear to be a small subset of the OS X APIs.
*: There may be some exceptions for managing VPNs, but this appears to be private API most likely granted special dispensation by Apple.
