Item 5 – Westermo RedFox Series User Manual
Page 665
Westermo OS Management Guide
Version 4.17.0-0
val can be configured in range 1-255 seconds. VRRPv3 allows sub-second
intervals (in steps of 100 ms) in range 0.1-40 seconds. All VRRP routers
associated with the same VRID must use the same VRRP version (see
), and must have the same advertisement interval setting.
A low VRRP advertisement interval gives faster fail-over (the time to detect
that a master is down is roughly 3 times the advertisement interval).
Default advertisement interval: 1 (second)
5. VRRP Priority: The VRRP priority parameter is used to define which router
should become master of the VIP address when multiple routers are avail-
able. (If two routers with the same priority transitions to master state, the
router with the highest IP address will win the election.)
The priority can be configured in range 1-255, where the value ”255” should
be used if (and only if) the router is also the owner of the VIP address (see
the Note in
above). Default priority: 100
WeOS supports dynamic VRRP priority. E.g., if the master router loses its
Internet connection it should lower its priority dynamically (or even decline
to be master), this to allow for a backup router to take over immediately.
For example, if R1 in
b would lose its upstream connection, it could
lower its priority to 30, whereby R2 would could take over if preemption is
enabled.
In WeOS, dynamic VRRP priority is configured by mapping the status of an
event trigger, typically a ping trigger (see
) to a priority adjust-
ment value.
If a router is the owner of the VIP, it should be configured with priority ”255”,
with dynamic priority disabled.
6. VRRP Preemption: The VRRP master election is not controlled by the priority
setting alone; there is also a preemption parameter, which enables you to
select to have a deterministic master election procedure (highest priority
always becomes master), or a sticky behaviour where the elected master
router would keep its role even when another router with higher priority
later appears on the network. With preemption disabled, the second router
would refrain from taking over as long as the current master continuous to
send advertisements.
The exception to this is if the new router connected to the subnet is the VIP
address owner (priority 255); the VIP owner will always preempt an existing
master.
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