Dell SmartFabric OS10 User Guide Release 10.5.3

BFD tracking support in VRRP groups

VRRP supports tracking BFD session objects in addition to tracking interface state objects.

The VRRP module supports BFD session tracking with configurable priority cost value using object tracking. When a BFD session goes DOWN, VRRP reduces the priority of the configured priority cost value, and the reduced priority value is used for any further advertisements. Similarly, when a BFD session is UP, the VRRP restores the priority value by adding the priority cost value to the current priority.

In conjunction with VRRP priority decrement using object tracking, priority decrement to value zero is supported. This behavior ensures VRRP to advertise priority zero packets to trigger immediate failover.

VRRP supports omitting skew time from the master_down_interval calculation formula as defined in RFC5798.

Skew time is the time to skew master_down_interval in seconds. Skew time is calculated using the following simple formula:

For VRRPv2:      (256 - Priority) / 256 )

For VRRPv3:      (((256 - priority) * Master_Adver_Interval) / 256)

You can reduce the time that is required to transition from the Standby state to the Active state by disabling the skew timer.