Network Failures; Understanding Vrrp - Juniper EX9200 Features Manual

CHAPTER 13
Understanding How the VRRP Router
Failover Mechanism Prevents Network
Failures

Understanding VRRP

Copyright © 2017, Juniper Networks, Inc.
Understanding VRRP on page 119
Junos OS Support for VRRPv3 on page 121
Improving the Convergence Time for VRRP on page 126
For Ethernet, Fast Ethernet, Gigabit Ethernet, 10-Gigabit Ethernet, and logical interfaces,
you can configure the Virtual Router Redundancy Protocol (VRRP) or VRRP for IPv6.
VRRP enables hosts on a LAN to make use of redundant routing platforms on that LAN
without requiring more than the static configuration of a single default route on the hosts.
The VRRP routing platforms share the IP address corresponding to the default route
configured on the hosts. At any time, one of the VRRP routing platforms is the master
(active) and the others are backups. If the master fails, one of the backup routers becomes
the new master router, providing a virtual default routing platform and enabling traffic
on the LAN to be routed without relying on a single routing platform. Using VRRP, a backup
router can take over a failed default router within a few seconds. This is done with
minimum VRRP traffic and without any interaction with the hosts.
Routers running VRRP dynamically elect master and backup routers. You can also force
assignment of master and backup routers using priorities from 1 through 255, with 255
being the highest priority. In VRRP operation, the default master router sends
advertisements to backup routers at regular intervals. The default interval is 1 second. If
a backup router does not receive an advertisement for a set period, the backup router
with the next highest priority takes over as master and begins forwarding packets.
NOTE: To minimize network traffic, VRRP is designed in such a way that only
the router that is acting as the master sends out VRRP advertisements at
any given point in time. The backup routers do not send any advertisement
until and unless they take over mastership.
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