OSPF Update Packet-Pacing Configurable Timers
Last Updated: May 4, 2009
This module describes the OSPF Update Packet-Pacing Configurable Timers feature, which allows you to configure the rate at which OSPF LSA flood pacing, retransmission pacing, and group pacing updates occur.
Finding Feature Information
For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for OSPF Update Packet-Pacing Configurable Timers" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS XE software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
•Restrictions on OSPF Update Packet-Pacing Configurable Timers
•Information About OSPF Update Packet-Pacing Configurable Timers
•How to Configure OSPF Packet-Pacing Timers
•Configuration Examples of OSPF Update Packet-Pacing
•Additional References
•Feature Information for OSPF Update Packet-Pacing Configurable Timers
Restrictions on OSPF Update Packet-Pacing Configurable Timers
Do not change the packet-pacing timers unless all other options to meet OSPF packet flooding requirements have been exhausted. Specifically, network operators should prefer summarization, stub area usage, queue tuning, and buffer tuning before changing the default timers. Furthermore, there are no guidelines for changing timer values; each OSPF deployment is unique and should be considered on a case-by-case basis. The network operator assumes risks that are associated with changing the default timer values.
Information About OSPF Update Packet-Pacing Configurable Timers
Before you change the OSPF update packet-pacing timers, you should understand the following concepts:
•Functionality of the OSPF Update Packet-Pacing Timers
•Benefits of OSPF Update Packet-Pacing Configurable Timers
Functionality of the OSPF Update Packet-Pacing Timers
In rare situations, you might need to change Open Shortest Path First (OSPF) packet-pacing default timers to mitigate CPU or buffer utilization issues associated with flooding very large numbers of link-state advertisements (LSAs). The OSPF Update Packet-Pacing Configurable Timers feature allows you to configure the rate at which OSPF LSA flood pacing, retransmission pacing, and group pacing updates occur.
•Configuring OSPF flood pacing timers allows you to control interpacket spacing between consecutive link-state update packets in the OSPF transmission queue.
•Configuring OSPF retransmission pacing timers allows you to control interpacket spacing between consecutive link-state update packets in the OSPF retransmission queue.
•Cisco IOS XE software groups the periodic refresh of LSAs to improve the LSA packing density for the refreshes in large topologies. The group timer controls the interval that is used for group LSA refreshment; however, this timer does not change the frequency at which individual LSAs are refreshed (the default refresh occurs every 30 minutes).
Caution
The default settings for OSPF packet-pacing timers are suitable for the majority of OSPF deployments. You should change the default timers only as a last resort.
Benefits of OSPF Update Packet-Pacing Configurable Timers
The OSPF Update Packet-Pacing Configurable Timers feature provides the administrator with a mechanism to control the rate at which LSA updates occur in order to reduce high CPU or buffer utilization that can occur when an area is flooded with a very large number of LSAs.
How to Configure OSPF Packet-Pacing Timers
The tasks in this section describe how to configure and verify three OSPF update packet-pacing timers.
•Configuring OSPF Packet-Pacing Timers (required)
•Verifying OSPF Packet-Pacing Timers (optional)
•Monitoring and Maintaining OSPF Packet-Pacing Timers (optional)
Configuring OSPF Packet-Pacing Timers
Caution
The default settings for OSPF packet-pacing timers are suitable for the majority of OSPF deployments. You should change the default timers only as a last resort.
To configure a flood packet-pacing timer, use the following commands beginning in global configuration mode:
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Step 1 |
Router(config)# router ospf process-id |
Places the router in router configuration mode and enables an OSPF routing process. |
Step 2 |
Router(config-router)# timers pacing flood milliseconds |
Configures a flood packet-pacing timer delay (in milliseconds). |
To configure a retransmission packet-pacing timer, use the following commands beginning in global configuration mode:
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Step 1 |
Router(config)# router ospf process-id |
Places the router in router configuration mode and enables an OSPF routing process. |
Step 2 |
Router(config-router)# timers pacing retransmission milliseconds |
Configures a retransmission packet-pacing timer delay (in milliseconds). |
To configure a group packet-pacing timer, use the following commands beginning in router configuration mode:
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Step 1 |
Router(config)# router ospf process-id |
Places the router in router configuration mode and enables an OSPF routing process. |
Step 2 |
Router(config-router)# timers pacing lsa-group seconds |
Configures an LSA group packet-pacing timer delay (in seconds). |
Verifying OSPF Packet-Pacing Timers
To verify that OSPF packet pacing has been configured, use the show ip ospf privileged EXEC command. The output of the show ip ospf command will display the type and delay time of the configurable pacing timers (flood, retransmission, group). The following sample output is from the show ip ospf command:
Routing Process "ospf 1" with ID 10.0.0.1 and Domain ID 10.20.0.1
Supports only single TOS(TOS0) routes
SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
LSA group pacing timer 100 secs
Interface flood pacing timer 55 msecs
Retransmission pacing timer 100 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 2. 2 normal 0 stub 0 nssa
External flood list length 0
Number of interfaces in this area is 2
Area has message digest authentication
SPF algorithm executed 4 times
Number of LSA 4. Checksum Sum 0x29BEB
Number of opaque link LSA 0. Checksum Sum 0x0
Number of DCbitless LSA 3
Number of indication LSA 0
Number of interfaces in this area is 0
Area has no authentication
SPF algorithm executed 1 times
192.168.0.0/16 Passive Advertise
Number of LSA 1. Checksum Sum 0x44FD
Number of opaque link LSA 0. Checksum Sum 0x0
Number of DCbitless LSA 1
Number of indication LSA 1
Troubleshooting Tips
If the number of OSPF packet retransmissions rapidly increases, increase the value of the packet-pacing timers. The number of OSPF packet retransmissions is displayed in the output of the show ip ospf neighbor command.
Monitoring and Maintaining OSPF Packet-Pacing Timers
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Router# show ip ospf |
Displays general information about OSPF routing processes. |
Router# show ip ospf neighbor |
Displays OSPF neighbor information on a per-interface basis. |
Router# clear ip ospf redistribution |
Clears route redistribution based on the OSPF routing process ID. |
Configuration Examples of OSPF Update Packet-Pacing
This section provides the following configuration examples:
•Example: LSA Flood Pacing
•Example: LSA Retransmission Pacing
•Example: LSA Group Pacing
Example: LSA Flood Pacing
The following example configures LSA flood pacing updates to occur in 50-millisecond intervals for OSPF routing process 1:
Router(config)# router ospf 1
Router(config-router)# timers pacing flood 50
Example: LSA Retransmission Pacing
The following example configures LSA retransmission pacing updates to occur in 100-millisecond intervals for OSPF routing process 1:
Router(config)# router ospf 1
Router(config-router)# timers pacing retransmission 100
Example: LSA Group Pacing
The following example configures OSPF group pacing updates between LSA groups to occur in 75-second intervals for OSPF routing process 1:
Router(config)# router ospf 1
Router(config-router)# timers pacing lsa-group 75
Additional References
For additional information related to the OSPF Update Packet-Pacing Configurable Timers feature, see the following references:
Related Documents
Standards
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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
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No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature. |
To locate and download MIBs for selected platforms, Cisco IOS XE software releases , and feature sets, use Cisco MIB Locator found at the following URL: http://www.cisco.com/go/mibs |
RFCs
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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
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The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
http://www.cisco.com/cisco/web/support/index.html |
Feature Information for OSPF Update Packet-Pacing Configurable Timers
Table 1 lists the release history for this feature.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note Table 1 lists only the Cisco IOS XE software release that introduced support for a given feature in a given Cisco IOS XE software release train. Unless noted otherwise, subsequent releases of that Cisco IOS XE software release train also support that feature.
Table 1 Feature Information for OSPF Update Packet-Pacing Configurable Timers
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OSPF Update Packet-Pacing Configurable Timers |
Cisco IOS XE Release 2.1 |
The OSPF Update Packet-Pacing Configurable Timers feature allows you to configure the rate at which OSPF LSA flood pacing, retransmission pacing, and group pacing updates occur. The following commands are introduced or modified in the feature documented in this module: •timers pacing flood •timers pacing lsa-group •timers pacing retransmission •show ip ospf |
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