OSPF Link-State Advertisement Throttling

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.

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Prerequisites for OSPF LSA Throttling

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

Information About OSPF LSA Throttling

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

Customizing OSPF LSA Throttling

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

Example:


LSAID: 10.1.1.1    Type: 1   Adv Rtr: 172.16.2.2 Due in: 00:00:00.028

Example:


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

Example:


Routing Process "ospf 4" with ID 10.10.24.4

Example:


 Supports only single TOS(TOS0) routes

Example:


 Supports opaque LSA

Example:


 Supports Link-local Signaling (LLS)

Example:


 Initial SPF schedule delay 5000 msecs

Example:


 Minimum hold time between two consecutive SPFs 10000 msecs

Example:


 Maximum wait time between two consecutive SPFs 10000 msecs

Example:


 Incremental-SPF disabled

Example:


 Initial  LSA  throttle  delay  100  msecs

Example:


            
              
                Minimum  hold  time  for  LSA  throttle  10000  msecs

Example:


            
              
                Maximum  wait  time  for  LSA  throttle  45000  msecs

Example:


Minimum LSA arrival 1000 msecs

Example:


 LSA group pacing timer 240 secs

Example:


 Interface flood pacing timer 33 msecs

Example:


 Retransmission pacing timer 66 msecs

Example:


 Number of external LSA 0. Checksum Sum 0x0

Example:


 Number of opaque AS LSA 0. Checksum Sum 0x0

Example:


 Number of DCbitless external and opaque AS LSA 0

Example:


 Number of DoNotAge external and opaque AS LSA 0

Example:


 Number of areas in this router is 1. 1 normal 0 stub 0 nssa

Example:


 External flood list length 0

Example:


    Area 24

Example:


        Number of interfaces in this area is 2

Example:


        Area has no authentication

Example:


        SPF algorithm last executed 04:28:18.396 ago

Example:


        SPF algorithm executed 8 times

Example:


        Area ranges are

Example:


        Number of LSA 4. Checksum Sum 0x23EB9

Example:


        Number of opaque link LSA 0. Checksum Sum 0x0

Example:


        Number of DCbitless LSA 0

Example:


        Number of indication LSA 0

Example:


        Number of DoNotAge LSA 0

Example:


        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

Example OSPF LSA Throttling

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: OSPF Command Reference

OSPFv3 Max-Metric Router LSA

“OSPFv3 Max-Metric Router LSA ” module

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.

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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.

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Technical Assistance

Description

Link

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