The flash-flood command enables LSP fast flooding to speed up IS-IS network convergence.
The undo flash-flood command disables LSP fast flooding.
By default, LSP fast flooding is disabled.
flash-flood [ lsp-count | max-timer-interval interval | [ level-1 | level-2 ] ] *
undo flash-flood [ lsp-count | max-timer-interval interval | [ level-1 | level-2 ] ] *
| Parameter | Description | Value |
|---|---|---|
| lsp-count | Specifies the maximum number of LSPs to be flooded at a time on an interface. | The value is an integer that ranges from 1 to 15. The default value is 5. |
| max-timer-interval interval | Specifies the maximum interval for LSP flooding. | The value is an integer that ranges from 10 to 50000, in milliseconds. The default value is 10 ms. |
| level-1 | Enables LSP fast flooding in Level-1. If no level is specified, by default, LSP fast flooding is enabled in both Level-1 and Level-2. | - |
| level-2 | Enables LSP fast flooding in Level-2. If no level is specified, by default, LSP fast flooding is enabled in both Level-1 and Level-2. | - |
In most cases, when an IS-IS router receives new LSPs from other routers, it updates the LSPs in its LSDB and periodically floods the updated LSPs according to a timer.
LSP fast flooding speeds up LSDB synchronization because it allows a device to flood fewer LSPs than the specified number before route calculation when the device receives one or more new LSPs. This mechanism also speeds up network convergence.
PrecautionsYou can specify the number of LSPs to be flooded each time. The number is valid for all IS-IS interfaces. If the number of LSPs to be flooded is greater than the specified value, the lsp-count number of the LSPs are sent. If the timer is configured and does not time out before route calculation, LSPs are flooded immediately; otherwise, LSPs are flooded when the timer times out.