Operation Manual – IPv4 RoutingH3C S7500E Series Ethernet Switches Chapter 4 IS-IS Configuration4-29To do… Use the command… RemarksAdd the interface to amesh groupisis mesh-group[ mesh-group-number |mesh-blocked ]OptionalNot added by defaultIf the mesh-blockedkeyword is included, theinterface is blocked fromflooding LSPs. It can sendan LSP only afterreceiving a request.Note:Note the following when enabling LSP fragment extension:z After LSP fragment extension is enabled in an IS-IS process, the MTUs of all theinterfaces with this IS-IS process enabled must not be less than 512; otherwise,LSP fragment extension will not take effect.z At least one virtual system needs to be configured for the router to generateextended LSP fragments.Note:z IS-IS messages cannot be fragmented at the IP layer because they are directlyencapsulated in frames. Therefore, IS-IS routers in an area need to send LSPssmaller than the smallest interface MTU in this area.z If the IS-IS routers have different interface MTUs, it is recommended to configurethe maximum size of generated LSP packets to be smaller than the smallestinterface MTU in this area. Otherwise, the routers have to dynamically adjust theLSP packet size to fit the smallest interface MTU, which takes time and affects otherservices.4.5.6 Configuring SPF ParametersWhen the LSDB changes in an IS-IS network, a routing calculation starts. If thechanges happen frequently, it will take a lot of system resources. You can set theinterval for SPF calculation for efficiency consideration.The SPF calculation may occupy the CPU for a long time when the routing entries aretoo many. You can split the SPF calculation time into multiple durations with a defaultinterval of 10s in between.Follow these steps to configure the SPF parameters:
