3Com Switch 8800 Configuration Guide Chapter 20 Integrated IS-IS Configuration
20-22
Perform the following configuration in IS-IS view.
Table 20-29 Set Lifetime of LSP
Operation Command
Set lifetime of LSP timer lsp-max-age seconds
Restore the default LSP lifetime undo timer lsp-max-age
By default, LSP can live for 1200 seconds (20 minutes).
20.2.23 Setting Parameters Related to SPF

I. Setting SPF calculation interval

When IS-IS LSDB changes, the router will compute the shortest path again. However,
the immediate calculation upon every change will occupy too many resources and
affect the efficiency of the router. In the case that SPF computing interval is set, when
LSDB changes, SPF algorithm will be run after the SPF interval times out.
Perform the following configuration in IS-IS view.
Table 20-30 Set SPF calculation interval
Operation Command
Set SPF calculation interval timer spf second [ level-1 | level-2 ]
Restore default SPF calculation interval undo timer spf [ level-1 | level-2 ]
If the level is not specified, it defaults to setting the SPF calculation interval of Level-1.
By default, SPF calculation runs every 10 seconds.

II. Setting SPF calculation in slice

When there is a large number of routes in the routing table (over 150,000), SPF
calculation of IS-IS may occupy the system resources for a long time. To prevent such a
case, SPF calculation can be set to perform in slice.
Perform the following configuration in IS-IS view.
Table 20-31 Set SPF calculation in slice
Operation Command
Set the duration of one cycle in second
of SPF calculation spf-slice-size seconds
Restore the default configuration undo spf-slice-size