Router Election Rules

If the master router becomes unavailable, the following rules govern election of the master router:

• The backup router assigned the highest priority for each VRID becomes the master router.
• If two backup routers were assigned the same priority, the router that has the highest primary address becomes the master router. For example, if several routers were all assigned the default priority of 100, the IP addresses must be compared.
• Router election on a VRRP router can also be determined by whether the preemption option is enabled.

  When a backup router detects a master router with a lower priority than the backup router has, the backup router might leave the current master router alone or take over the current master router and become the master router itself.

  When preemption is enabled, a backup router always preempts or takes over the responsibility of the master router. When preemption is disabled, the lower-priority backup is left in the master state.

  Note: Using VRRP can override the source address of the ICMP redirect. When a backup VRID functions as a master router on a given IP interface, its ICMP redirects must fake the source IP address of the IP address owner. The redirect must fake the IP address because hosts accept only an ICMP redirect that is sent by the current gateway of the host.

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