Dell S6100 Configuration Manual page 902

Usage Information
This command spf-interval in CONFIG-ROUTER-ISIS-AF-IPV6 mode is used for IPv6 Multi-Topology route
computation only. If using Single Topology mode, use the spf-interval command in CONFIG-ROUTER-ISIS
mode for both IPv4 and IPv6 route computations.
SPF throttling slows down the frequency at which route calculations are performed during network instability. Even
though throttling route calculations slows down network convergence, not throttling can result in a network not
functioning as expected. If network topology is unstable, throttling slows down the scheduling of route calculations
until the topology regains its stability.
The first route calculation is controlled by the initial wait interval and the second calculation is controlled by the
second wait interval. Each subsequent wait interval is twice as long as the previous one until the wait interval
reaches the maximum wait time specified (interval seconds). After the network calms down and there are
no triggers for two times the maximum interval, fast behavior is restored (the initial wait time).
902 Intermediate System to Intermediate System (IS-IS)