Carp

http://www.gentoo-wiki.info/HOWTO_Setup_IP_failover_with_UCARP examples for config scripts for ucarp daemon. ucap is a alternative for VRRP, alows 2 devices to have shared IP address. used for setup redundant routers, load balancers

http://tservice.net.ru/~s0mbre/old/?section=projects&item=carp CARP is an improved version of the Virtual Router Redundancy Protocol (VRRP) standard. It has more features than Cisco’s HSRP. There is another[user-space] implementation called ucarp. This version does not compartable with OpenBSD CARP.