Solaris is another step closer to the complete implementation of Project Crossbow. On 19 January, the IP Instance project was integrated into Nevada with the intentions of making IP Instances available through S10U4.
From the "IP Instances Interface Document":
IP instances introduces the ability to have separate zones connected to separate LANs or VLANs without introducing any network security issues. It does this by applying a simple approach to separate all the previously global variables in the TCP/IP collection of kernel modules, so that there can be multiple instances of them, and by providing some extensions to zonecfg to specify that a zone should have its own IP instance.
You can find more details on how to configure this is in the Project Crossbow docs.