TP-Link JetStream T2700G-28TQ User Manual page 224

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

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 router
is assigned as the default gateway for the hosts within the LAN. Communication with external
network can be realized via the virtual router.
Master router is selected from the physical routers in the virtual router group according to
VRRP priority. The elected master router provides routing service to the hosts in LAN, and
sends VRRP messages periodically to publicize its configuration information like priority and
operating condition to other routers in backup group. Other physical routers in the backup
group work as backup routers. They monitor the VRRP packets sent by the master router. A
new master router will be elected among them to take the role of the master router if master
router fails.
2. Master Election
Initially-created routers work in Backup state and learn other members' priorities in the virtual
router via VRRP packets. The one with the highest priority is elected as master router. If the
priority values are the same, the router with the highest interface IP address is selected as the
master.
In preemptible mode, when backup router receives VRRP packet, it will compare its priority
•
with that of the advertisement packet. If of higher priority, the backup router will become
the master router; otherwise, it will maintain Backup state.
In non-preemptible mode, physical routers in the backup group will maintain Master or
•
Backup state as long as the master router functions normally. Even if backup router is
given higher priority, it cannot become a master router in non-preempt mode.
Figure 10-57 Typical Networking Application Diagram
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