Defining The Spf Route Calculation Level - Juniper IGP - CONFIGURATION GUIDE V11.1.X Configuration Manual

JUNOSe 11.0.x IP, IPv6, and IGP Configuration Guide
and so on. When the maximum configured interval is reached, the interval reverts
back to immediate response mode for the next triggering event.
If no calculation-triggering network events have occurred by the end of any given
back-off interval, the router reverts back to immediate response mode.
spf-interval

Defining the SPF Route Calculation Level

The IS-IS protocol uses the Dijkstra algorithm to compute IP node metrics when a
change occurs within the IS-IS network. This calculation results in the IS-IS router
containing a shortest-path tree (SPT) that maps the shortest path to each node in the
IS-IS network.
By default, the router uses a partial route calculation (PRC) SPF to determine the next
hop (when required). This partial computation occurs when the router receives
link-state PDUs (LSPs) with only changes relating to IP prefixes (for example, the
addition of a new IP prefix, change in attributes of an existing IP prefix, or the removal
of an existing IP prefix).
Because changes in IP prefixes happen more frequently than other events, using the
PRC SPF results in faster IS-IS convergence and saves router resources. However,
you can also specify that the router always use full SPF, recalculating the entire SPT,
when resolving any IS-IS state changes.
full-spf-always
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Configuring Global IS-IS Parameters
Use to set the maximum interval between SPF calculations.
You can select an interval value in the range 0–120 seconds.
The default value is 5 seconds.
If you do not specify level-1 or level-2, the interval applies to both level 1 and
level 2.
SPF calculations are performed only when the topology of the area changes.
They are not performed when external routes change.
Example
host1(config-router)#spf-interval level-2 30
Use the no version to restore the default value, 5 seconds.
See spf-interval
Use to enable and disable full SPF calculations for IS-IS network changes.
Example
host1(config-router)#full-spf-always
Use the no version to restore partial route calculation (PRC) mode for SPF
calculations.
See full-spf-always