I am constantly configuring firewalls and wireless access points for clients.  It has always been a pain to have to go offline for a while, while I switch the computer to use a different IP address while I’m configuring the device.  Today I was put in the same situation, except this time I’m using a Mac, and have a solution!

Its very simple, this is how its done:

• Go to System Preferences, Network
• Click the + symbol at the bottom of the device list to create a new interface
• On the interface selection, choose ethernet
• In the Service Name section, enter whatever you want to call the second interface, in my case Ethernet 2

Thats it!  Your done.  You can now configure the new interface to use whatever IP address you want and configure your device without leaving your native network.  Of course, this can also be done using your wireless interface as well.