redundant interface will not fail over

[Guest]

[bcarrier]

I'm running 2.4 and I added a new connection under network and interfaces. I added a DHCP internet connection that's running on eth3. I tested this on a different endian box as the red interface and it worked. I set this connection as a back up for fail over but when I try unplugging the main red connection it doesn't fail over to the second connection.