Table Of Contents

OSPF Link-State Advertisement Throttling

Contents

Prerequisites for OSPF LSA Throttling

Information About OSPF LSA Throttling

Benefits of OSPF LSA Throttling

How OSPF LSA Throttling Works

How to Customize OSPF LSA Throttling

Customizing OSPF LSA Throttling

Configuration Examples for OSPF LSA Throttling

OSPF LSA Throttling: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

OSPF Link-State Advertisement Throttling

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The OSPF Link-State Advertisement (LSA) Throttling feature provides a dynamic mechanism to slow down link-state advertisement (LSA) updates in OSPF during times of network instability. It also allows faster Open Shortest Path First (OSPF) convergence by providing LSA rate limiting in milliseconds.

History for the OSPF LSA Throttling Feature

Release	Modification
12.0(25)S	This feature was introduced.
12.3(2)T	This feature was integrated into Cisco IOS Release 12.3(2)T.
12.2(18)S	This feature was integrated into Cisco IOS Release 12.2(18)S.
12.2(27)SBC	This feature was integrated into Cisco IOS Release 12.2(27)SBC.

Finding Support Information for Platforms and Cisco IOS Software Images

Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.

Contents

•Prerequisites for OSPF LSA Throttling

•Information About OSPF LSA Throttling

•How to Customize OSPF LSA Throttling

•Configuration Examples for OSPF LSA Throttling

•Additional References

•Command Reference

Prerequisites for OSPF LSA Throttling

It is presumed that you have OSPF configured in your network.

Information About OSPF LSA Throttling

Before you enable OSPF LSA Throttling, you should understand the following concepts:

•Benefits of OSPF LSA Throttling

•How OSPF LSA Throttling Works

Benefits of OSPF LSA Throttling

Prior to the OSPF LSA Throttling feature, LSA generation was rate-limited for 5 seconds. That meant that changes in an LSA could not be propagated in milliseconds, so the OSPF network could not achieve millisecond convergence.

The OSPF LSA Throttling feature is enabled by default and allows faster OSPF convergence (in milliseconds). This feature can be customized. One command controls the generation (sending) of LSAs and another command controls the receiving interval. This feature also provides a dynamic mechanism to slow down the frequency of LSA updates in OSPF during times of network instability.

How OSPF LSA Throttling Works

The timers throttle lsa all command controls the generation (sending) of LSAs. The first LSA is always generated immediately upon an OSPF topology change, and the next LSA generated is controlled by the minimum start interval. The subsequent LSAs generated for the same LSA are rate-limited until the maximum interval is reached. The "same LSA" is defined as an LSA instance that contains the same LSA ID number, LSA type, and advertising router ID.

The timers lsa arrival command controls the minimum interval for accepting the same LSA. If an instance of the same LSA arrives sooner than the interval that is set, the LSA is dropped. It is recommended that the arrival interval be less than or equal to the hold-time interval of the timers throttle lsa all command.

How to Customize OSPF LSA Throttling

This section contains the following optional procedure:

•Customizing OSPF LSA Throttling (optional)

Customizing OSPF LSA Throttling

This task describes how to customize OSPF LSA throttling if you prefer to set values other than the defaults.

SUMMARY STEPS

1. enable

2. configure terminal

3. router ospf process-id

4. timers throttle lsa all start-interval hold-interval max-interval

5. timers lsa arrival milliseconds

6. end

7. show ip ospf timers rate-limit

8. show ip ospf

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	router ospf process-id Example: Router(config)# router ospf 1	Configures an OSPF routing process.
Step 4	timers throttle lsa all start-interval hold-interval max-interval Example: Router(config-router)# timers throttle lsa all 100 10000 45000	(Optional) Sets the rate-limiting values (in milliseconds) for LSA generation. •The default values are as follows: –start-interval is 0 milliseconds –hold-interval is 5000 milliseconds –max-interval is 5000 milliseconds
Step 5	timers lsa arrival milliseconds Example: Router(config-router)# timers lsa arrival 2000	(Optional) Sets the minimum interval (in milliseconds) between instances of receiving the same LSA. •The default value is 1000 milliseconds. •We suggest you keep the milliseconds value of the LSA arrival timer less than or equal to the neighbors' hold-interval value of the timers throttle lsa all command.
Step 6	end Example: Router(config-router)# end	Exits router configuration mode.
Step 7	show ip ospf timers rate-limit Example: Router# show ip ospf timers rate-limit LSAID: 10.1.1.1    Type: 1   Adv Rtr: 172.16.2.2 Due in: 00:00:00.028 LSAID: 192.168.4.1   Type: 3   Adv Rtr: 172.17.2.2 Due in: 00:00:00.028	(Optional) Displays a list of the LSAs in the rate limit queue (about to be generated). •The example shows two LSAs in the queue. Each LSA is identified by LSA ID number, Type (of LSA), Advertising router ID, and the time in hours:minutes:seconds (to the milliseconds) when the LSA is due to be generated.
Step 8	show ip ospf Example: Router# show ip ospf Routing Process "ospf 4" with ID 10.10.24.4 Supports only single TOS(TOS0) routes Supports opaque LSA Supports Link-local Signaling (LLS) Initial SPF schedule delay 5000 msecs Minimum hold time between two consecutive SPFs 10000 msecs Maximum wait time between two consecutive SPFs 10000 msecs Incremental-SPF disabled Initial LSA throttle delay 100 msecs Minimum hold time for LSA throttle 10000 msecs Maximum wait time for LSA throttle 45000 msecs Minimum LSA arrival 1000 msecs LSA group pacing timer 240 secs Interface flood pacing timer 33 msecs Retransmission pacing timer 66 msecs Number of external LSA 0. Checksum Sum 0x0 Number of opaque AS LSA 0. Checksum Sum 0x0 Number of DCbitless external and opaque AS LSA 0 Number of DoNotAge external and opaque AS LSA 0 Number of areas in this router is 1. 1 normal 0 stub 0 nssa External flood list length 0 Area 24 Number of interfaces in this area is 2 Area has no authentication SPF algorithm last executed 04:28:18.396 ago SPF algorithm executed 8 times Area ranges are Number of LSA 4. Checksum Sum 0x23EB9 Number of opaque link LSA 0. Checksum Sum 0x0 Number of DCbitless LSA 0 Number of indication LSA 0 Number of DoNotAge LSA 0 Flood list length 0	(Optional) Displays information about OSPF. •The output lines shown in bold in the example indicate the LSA throttling values.

Configuration Examples for OSPF LSA Throttling

This section contains an example of customizing OSPF LSA throttling:

•OSPF LSA Throttling: Example

OSPF LSA Throttling: Example

This example customizes OSPF LSA throttling so that the start interval is 200 milliseconds, the hold interval is 10,000 milliseconds, and the maximum interval is 45,000 milliseconds. The minimum interval between instances of receiving the same LSA is 2000 milliseconds.

router ospf 1

 log-adjacency-changes

 timers throttle lsa all 200 10000 45000

 timers lsa arrival 2000

 network 10.10.4.0 0.0.0.255 area 24

 network 10.10.24.0 0.0.0.255 area 24

Additional References

The following sections provide references related to OSPF LSA throttling.

Related Documents

Related Topic	Document Title
OSPF commands	Cisco IOS IP Routing Protocols Command Reference

Standards

Standards	Title
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.	—

MIBs

MIBs	MIBs Link
None	To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: http://www.cisco.com/go/mibs

RFCs

RFCs	Title
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.	—

Technical Assistance

Description	Link
The Cisco Technical Support website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.	http://www.cisco.com/techsupport

Command Reference

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS IP Routing Protocols Command Reference at http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_book.html. For information about all Cisco IOS commands, go to the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or to the Cisco IOS Master Commands List.

•debug ip ospf database-timer rate-limit

•show ip ospf

•show ip ospf timers rate-limit

•timers lsa arrival

•timers throttle lsa all

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