H3C S7500E Series Ethernet Switches Operation Manual

Operation Manual – IPv4 Routing
H3C S7500E Series Ethernet Switches Chapter 4 IS-IS Configuration
4-29
To do… Use the command… Remarks
Add the interface to a
mesh group
isis mesh-group
[ mesh-group-number |
mesh-blocked ]
Optional
Not added by default
If the mesh-blocked
keyword is included, the
interface is blocked from
flooding LSPs. It can send
an LSP only after
receiving 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 the
interfaces 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 generate
extended LSP fragments.
 Note:
z IS-IS messages cannot be fragmented at the IP layer because they are directly
encapsulated in frames. Therefore, IS-IS routers in an area need to send LSPs
smaller than the smallest interface MTU in this area.
z If the IS-IS routers have different interface MTUs, it is recommended to configure
the maximum size of generated LSP packets to be smaller than the smallest
interface MTU in this area. Otherwise, the routers have to dynamically adjust the
LSP packet size to fit the smallest interface MTU, which takes time and affects other
services.
4.5.6 Configuring SPF Parameters
When the LSDB changes in an IS-IS network, a routing calculation starts. If the
changes happen frequently, it will take a lot of system resources. You can set the
interval for SPF calculation for efficiency consideration.
The SPF calculation may occupy the CPU for a long time when the routing entries are
too many. You can split the SPF calculation time into multiple durations with a default
interval of 10s in between.
Follow these steps to configure the SPF parameters: