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2.
Specify the LSP refresh interval and generation interval
Each router needs to refresh LSPs generated by itself at a configurable interval and send them to other
routers to prevent valid routes from being aged out. A smaller refresh interval speeds up network
convergence but consumes more bandwidth.
When the network topology changes, for example, a neighbor is down or up, or the interface metric,
system ID, or area ID is changed, the router generates an LSP after a configurable interval. If such a
change occurs frequently, excessive LSPs are generated, consuming a large amount of router resources
and bandwidth. To solve the problem, you can adjust the LSP generation interval.
Follow these steps to specify the LSP refresh interval and generation interval:
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 LSP refresh interval
timer lsp-refresh
seconds
Optional
900 seconds by
default
Specify the LSP generation
interval
timer lsp-generation
maximum-interval
[
initial-interval
[
second-wait-interval
] ] [
level-1
|
level-2
]
Optional
2 seconds by default
3.
Specify LSP sending intervals
If a change occurs in the LSDB, IS-IS advertises the changed LSP to neighbors. You can specify the
minimum interval for sending such LSPs.
On a P2P link, IS-IS requires an advertised LSP be acknowledged. If no acknowledgement is received
within a configurable interval, IS-IS will retransmit the LSP.
Follow these steps to configure LSP sending intervals:
To do…
Use the command…
Remarks
Enter system view
system-view
—
Enter interface view
interface
interface-type
interface-number
—
Specify the minimum interval for
sending LSPs and the maximum LSP
number that can be sent at a time
isis timer lsp
time
[
count
count
]
Optional
By default, the minimum interval is 33
milliseconds, and the maximum LSP
number that can be sent at a time is 5.
Specify the LSP retransmission
interval on a P2P link
isis timer retransmit
seconds
Optional
5 seconds by default
NOTE:
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.
IS-IS routers in an area must send LSPs smaller than the smallest interface MTU in this area.
