H3C Technologies H3C S7500E Series Switches - Manual (Page 175)

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Configure a proper LSP retransmission interval to avoid unnecessary retransmissions.
Specifying LSP lengths
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.
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.
Follow these steps to specify LSP lengths:
To do… Use the command… Remarks
Enter system view system-view ––
Enter IS-IS view
isis [ process-id ] [ vpn-instance
vpn-instance-name ]
––
Specify the maximum length of
generated Level-1 LSPs or Level-2
LSPs
lsp-length originate size [ level-1 | level-2 ] 1497 bytes by default
Specify the maximum length of
received LSPs
lsp-length receive size 1497 bytes by default
Enabling LSP flash flooding
Since changed LSPs may trigger SPF recalculation, you can enable LSP flash flooding to advertise the
changed LSPs before the router recalculates routes. Doing so can speed up network convergence.
Follow these steps to enable LSP flash flooding:
To do… Use the command… Remarks
Enter system view system-view ––
Enter IS-IS view isis [ process-id ] [ vpn-instance vpn-instance-name ] ––
Enable LSP flash flooding
flash-flood [ flood-count flooding-count |
max-timer-interval flooding-interval | [ level-1 |
level-2 ] ] *
Required
Not enabled by
default
Enabling LSP fragment extension
Follow these steps to enable LSP fragment extension: