The ability to test and debug your title in an environment without a connection to the Internet or to Xbox Live is critical to ensuring that your title will behave correctly when these network-down situations occur in the real world.
The xbstress tool allows your development kit to simulate a situation where it is unplugged or otherwise unable to connect to the internet. This eliminates the need to physically set up a network which is not connected to the internet or use a PC with multiple network cards to simulate a no connectivity situation.
network=broken.
xbstress simulate network=broken
xbstress stop.See Network stress for additional information on using xbstress.