H3C Technologies H3C S12500 Series Switches - Manual (Page 173)

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Step Command Remarks
4. Specify the LSP
retransmission interval on a
P2P link.
isis timer retransmit seconds
Optional.
5 seconds by default.
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 must send LSPs smaller than the smallest interface MTU in this area.
If the IS-IS routers have different interface MTUs, H3C recommends configuring the maximum size of
generated LSP packets to be smaller than the smallest interface MTU in this area. Otherwise, the routers
must dynamically adjust the LSP packet size to fit the smallest interface MTU, which takes time and affects
other services.
To specify LSP lengths:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter IS-IS view.
isis [ process-id ] [ vpn-instance
vpn-instance-name ]
N/A
3. Specify the maximum length
of generated Level-1 LSPs or
Level-2 LSPs.
lsp-length originate size [ level-1 | level-2 ]
Optional.
1497 bytes by default.
4. Specify the maximum length
of received LSPs.
lsp-length receive size
Optional.
1497 bytes by default.
Enabling LSP flash flooding
Changed LSPs can trigger SPF recalculation. To advertise the changed LSPs before the router recalculates
routes for faster network convergence, enable LSP flash flooding.
To enable LSP flash flooding:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter IS-IS view. isis [ process-id ] [ vpn-instance vpn-instance-name ] N/A
3. Enable LSP flash
flooding.
flash-flood [ flood-count flooding-count |
max-timer-interval flooding-interval | [ level-1 |
level-2 ] ] *
Not enabled by
default.
Enabling LSP fragment extension
After LSP fragment extension is enabled for an IS-IS process, the MTUs of all the interfaces running the
IS-IS process must not be less than 512; otherwise, LSP fragment extension will not take effect.
At least one virtual system must be configured for the router to generate extended LSP fragments. An IS-IS
process allows a maximum of 50 virtual systems.
To enable LSP fragment extension: