ucarp
From thelinuxwiki
http://forums.gentoo.org/viewtopic-t-936898-start-0.html
failing over multiple interfaces together
net.inet.carp.preempt Allow virtual hosts to preempt each other. It is also used to failover carp interfaces as a group. When the option is enabled and one of the carp enabled physical interfaces goes down, advskew is changed to 240 on all carp inter- faces. See also the first example. Disabled by default.