ucarp

Userlevel Common Address Redundancy Protocol

UCARP allows a couple of hosts to share common virtual IP addresses in order to provide automatic failover. It is a portable userland implementation of the secure and patent-free Common Address Redundancy Protocol (CARP, OpenBSD's alternative to the VRRP). Because UCARP does not require "promiscuous mode" on interfaces, it may be a suitable option in environments where carp(4) may be difficult to deploy, such as in clouds or other virtualized infrastructures.