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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.
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