VRRP daemon (vrrpd) is an RFC 2338 compliant implementation of
the Virtual Router Redundancy Protocol (VRRP). The Virtual Router
Redundancy Protocol is designed to eliminate the single point of
failure associated with statically routed networks by automatically
providing failover using multiple LAN paths through alternate routers.

As specified in RFC 2338, VRRP uses an election protocol that
dynamically assigns responsibility for a virtual router to one of the
VRRP routers on a LAN. When a VRRP router controls the IP address(es)
associated with a virtual router, it is called the Master. The Master
continues to forward packets sent to these IP addresses until it has a
problem that causes the VRRP routers to hold an election. The election
process provides dynamic failover by electing a new Master should the
existing Master become unavailable.

The virtual router associated with each alternate path under VRRP uses
the same IP address and MAC address as the routers for other paths. As
a result, the host's gateway information does not change, no matter
what path is used.  Because of this design, VRRP-based redundancy
significantly reduces administrative overhead when compared to
redundancy schemes that require hosts to be configured with multiple
default gateways.

The primary function of the Virtual Router Redundancy Protocol is to
provide routing redundancy for specific IP addresses. In addition to
this primary function, RFC 2338 also states that the protocol should:

 * Minimize the duration of black holes.
 * Minimize the steady state bandwidth overhead and processing
   complexity.
 * Function over a variety of multiaccess LAN technologies that support
   IP traffic.
 * Provide for election of multiple virtual routers on a network for
   load balancing.
 * Support multiple logical IP subnets on a single LAN segment.