Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 294)

266 Multi-Service IronWare Routing Configuration Guide
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Globally configuring IS-IS on a device
Disabling incremental SPF optimizations
In the event of certain topology changes (for instance non-local adjacency flaps), IS-IS employs
incremental SPF optimizations to efficiently update the routing table. An incremental SPF is faster
and takes fewer CPU cycles than a full SPF.
You can optionally configure IS-IS to perform a full SPF calculation when any network topology
change occurs by using the disable-incremental-spf-opt command. When
disable-incremental-spf-opt is configured, IS-IS always runs full SPF for all such network topology
changes.
To disable incremental SPF optimizations for IS-IS, enter the following command.
Brocade(config-isis-router)# disable-incremental-spf-opt
Syntax: [no] disable-incremental-spf-opt
To restore incremental SPF optimizations, use the no form of this command.
NOTE
If you disable the partial SPF optimizations (by using the disable-partial-spf-opt command), IS-IS
automatically disables the incremental SPF optimizations and always runs full SPF, too. However, the
reverse is not true: disabling incremental SPF optimizations does not disable partial optimizations.
IS-IS incremental shortcut LSP SPF optimization
IS-IS can be configured to use an incremental shortcut LSP SPF optimization algorithm.
Incremental shortcut LSP SPF optimization is more efficient when updating the routes in cases
where the shortcut LSP state change does not influence the topology. Incremental Shortcut LSP
SPF Optimizations are on by default.
NOTE
If you disable the partial SPF optimizations (by using the disable-partial-spf-opt command), IS-IS
automatically disables the incremental SPF optimizations and always runs full SPF, too. However, the
reverse is not true: disabling incremental SPF optimizations does not disable partial optimizations.
Configuration considerations
Incremental Shortcut SPF optimizations will not be applicable to LSP shortcuts with metrics
configured on them
Incremental Shortcut SPF optimizations will not be applicable to LSP shortcuts with negative
relative metrics configured.
Incremental Shortcut SPF optimizations will not be applicable to announced LSP shortcuts.
DIsabling IS-IS Incremental Shortcut LSP SPF Optimization
To disable incremental shortcut LSP SPF optimization, enter the following commands at the global
configuration mode.
Brocade((config)#router isis
Brocade(config-isis-router)#disable-inc-stct-spf-opt
Syntax: [no] disable--inc-stct-spf-opt