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VRRP is developed to solve the problem mentioned above and designed for LAN with multicast
or broadcast function, such as Ethernet. Virtual router acts as a backup group which consists
of one master router and several backup routers.
The virtual router (also a backup group) has its own IP address. This IP address can be the same
as the interface address of any router in the backup group. In this case, the virtual router is also
called IP address owner. All physical routers in the backup group have their own IP addresses.
Hosts in LAN only recognize the IP address of the virtual router, but not that of the master
router or backup routers. The IP address of the virtual router is assigned as the default gateway
for the participating routers. Hosts in LAN communicate with external network via the virtual
router. Once the master router in backup group fails, another router will be selected to replace
it from the backup group through election protocol and thus provides routing service for hosts.
Therefore, communication between hosts and external network can be established without
interruption.
Advantages of VRRP
VRRP owns the following advantages:
1.
Simplified network management. In LAN with multicast or broadcast function, such as
Ethernet, even though a device fails, with the help of VRRP, highly-reliable default link can
still be provided and network interruption can be avoided after a single link fails without
reconfiguration of dynamic routing or router discovery protocols, or default gateway
configuration on every end-host.
2.
Small network overhead. The single message that VRRP defines is the VRRP
advertisement, which can only be sent by the master router.
Typical Networking Application Diagram
Figure 10-58 Typical Networking Application Diagram
VRRP Operating Principle
1.
Working Process
VRRP backup group, or virtual router, consists of a group of physical routers with the same
VRID (virtual route identifier). A virtual router owns one or more virtual IP addresses and one
virtual MAC address, in the format 00-00-5E-00-01-{VRID}. The IP address of the virtual
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