Cisco IOS IP Routing Protocols Configuration Guide, Release 12.2SR
OSPF Link-State Database Overload Protection
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Table Of Contents

OSPF Link-State Database Overload Protection

Contents

Prerequisites for OSPF Link-State Database Overload Protection

Information About OSPF Link-State Database Overload Protection

Benefits of Using OSPF Link-State Database Overload Protection

How OSPF Link-State Database Overload Protection Works

How to Configure the OSPF Link-State Database Overload Protection Feature

Limiting the Number of Self-Generating LSAs for an OSPF Process

Verifying the Number of Nonself-Generated LSAs on a Router

Configuration Examples for the OSPF Link-State Database Overload Protection Feature

Setting a Limit for LSA Generation: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

Glossary


OSPF Link-State Database Overload Protection

The OSPF Link-State Database Overload Protection feature allows you to limit the number of nonself-generated link-state advertisements (LSAs) for a given Open Shortest Path First (OSPF) process. Excessive LSAs generated by other routers in the OSPF domain can substantially drain the CPU and memory resources of the router.

History for the OSPF Link-State Database Overload Protection Feature

Release
Modification

12.0(27)S

This feature was introduced.

12.3(7)T

This feature was integrated into Cisco IOS Release 12.3(7)T.

12.2(25)S

This feature was integrated into Cisco IOS Release 12.2(25)S.

12.2(18)SXE

This feature was integrated into Cisco IOS Release 12.2(18)SXE.

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 Link-State Database Overload Protection

•Information About OSPF Link-State Database Overload Protection

•How to Configure the OSPF Link-State Database Overload Protection Feature

•Configuration Examples for the OSPF Link-State Database Overload Protection Feature

•Additional References

•Command Reference

Prerequisites for OSPF Link-State Database Overload Protection

It is presumed you have OSPF running on your network.

Information About OSPF Link-State Database Overload Protection

Before you configure the OSPF Link-State Database Overload Protection feature, you should understand the concepts described in the following sections:

•Benefits of Using OSPF Link-State Database Overload Protection

•How OSPF Link-State Database Overload Protection Works

Benefits of Using OSPF Link-State Database Overload Protection

The OSPF Link-State Database Overload Protection feature provides a mechanism at the OSPF level to limit the number of nonself-generated LSAs for a given OSPF process. When other routers in the network have been misconfigured, they may generate a high volume of LSAs, for instance, to redistribute large numbers of prefixes. This protection mechanism prevents routers from receiving a large number of LSAs and therefore experiencing CPU and memory shortages.

How OSPF Link-State Database Overload Protection Works

When the OSPF Link-State Database Overload Protection feature is enabled, the router keeps a count of the number of received (nonself-generated) LSAs it has received. When the configured threshold number of LSAs is reached, an error message is logged. When the configured maximum number of LSAs is exceeded, the router will send a notification. If the count of received LSAs is still higher than the configured maximum after one minute, the OSPF process takes down all adjacencies and clears the OSPF database. In this ignore state, all OSPF packets received on any interface that belongs to this OSPF process are ignored and no OSPF packets are generated on any of these interfaces. The OSPF process remains in the ignore state for the time configured by the ignore-time keyword of the max-lsa command. Each time the OSPF process gets into an ignore state a counter is incremented. If this counter exceeds the number counts configured by the ignore-count keyword, the OSPF process stays permanently in the same ignore state and manual intervention is required to get the OSPF process out of the ignore state. The ignore state counter is reset to 0 when the OSPF process remains in the normal state of operation for the amount of time that was specified by the reset-time keyword.

If the warning-only keyword of the max-lsa command has been configured, the OSPF process will send only a warning that the LSA maximum has been exceeded.

How to Configure the OSPF Link-State Database Overload Protection Feature

This section contains the following procedure:

•Limiting the Number of Self-Generating LSAs for an OSPF Process (required)

Limiting the Number of Self-Generating LSAs for an OSPF Process

This task describes how to configure and verify a limit on the number of nonself-generating LSAs for an OSPF process.

SUMMARY STEPS

1. enable

2. configure terminal

3. router ospf process-id

4. router-id ip-address

5. log-adjacency-changes [detail]

6. max-lsa maximum-number [threshold-percentage] [warning-only] [ignore-time minutes] [ignore-count count-number] [reset-time minutes]

7. network ip-address wildcard-mask area area-id

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

Enables OSPF routing.

•The process-id argument identifies the OSPF process.

Step 4 

router-id ip-address

Example:

Router(config-router)# router-id 10.0.0.1

Specifies a fixed router ID for an OSPF process.

Step 5 

log-adjacency-changes [detail]

Example:

Router(config-router)# log-adjacency-changes

Configures the router to send a syslog message when an OSPF neighbor goes up or down.

Step 6 

max-lsa maximum-number [threshold-percentage] [warning-only] [ignore-time minutes] [ignore-count count-number] [reset-time minutes]

Example:

Router(config-router)# max-lsa 12000

Limits the number of nonself-generated LSAs an OSPF routing process can keep in the OSPF link-state database (LSDB).

Step 7 

network ip-address wildcard-mask area area-id

Example:

Router(config-router)# network 209.165.201.1 255.255.255.255 area 0

Defines the interfaces on which OSPF runs and defines the area ID for those interfaces.

Verifying the Number of Nonself-Generated LSAs on a Router

The show ip ospf command is entered with the database-summary keyword to verify the actual number of nonself-generated LSAs on a router. This command can be used at any given point in time to display lists of information related to the OSPF database for a specific router. 

Router# show ip ospf 2000 database database-summary 


             OSPF Router with ID (192.168.1.3) (Process ID 2000)


Area 0 database summary

  LSA Type      Count    Delete   Maxage

  Router        5        0        0       

  Network       2        0        0       

  Summary Net   8        2        2       

  Summary ASBR  0        0        0       

  Type-7 Ext    0        0        0       

    Prefixes redistributed in Type-7  0

  Opaque Link   0        0        0       

  Opaque Area   0        0        0       

  Subtotal      15       2        2       


Process 2000 database summary

  LSA Type      Count    Delete   Maxage

  Router        5        0        0       

  Network       2        0        0       

  Summary Net   8        2        2       

  Summary ASBR  0        0        0       

  Type-7 Ext    0        0        0       

  Opaque Link   0        0        0       

  Opaque Area   0        0        0       

  Type-5 Ext    4        0        0       

    Prefixes redistributed in Type-5  0

  Opaque AS     0        0        0       

  Non-self      16      

  Total         19       2        2

Configuration Examples for the OSPF Link-State Database Overload Protection Feature

This section contains the following example:

•Setting a Limit for LSA Generation: Example

Setting a Limit for LSA Generation: Example

In the following example, the router is configured to not accept any more nonself-generated LSAs once a maximum of 14,000 has been exceeded: 

Router(config)# router ospf 1

Router(config-router)# router-id 192.168.0.1

Router(config-router)# log-adjacency-changes

Router(config-router)# max-lsa 14000

Router(config-router)# area 33 nssa

Router(config-router)# network 192.168.0.1 0.0.0.0 area 1

Router(config-router)# network 192.168.5.1 0.0.0.0 area 1

Router(config-router)# network 192.168.2.1 0.0.0.0 area 0

In the following example, the show ip ospf command has been entered to confirm the configuration: 

Router# show ip ospf 1


Routing Process "ospf 1" with ID 192.168.0.1

Supports only single TOS(TOS0) routes

Supports opaque LSA

Supports Link-local Signaling (LLS)

Supports area transit capability

Maximum number of non self-generated LSA allowed 14000

   Threshold for warning message 75%

   Ignore-time 5 minutes, reset-time 10 minutes

   Ignore-count allowed 5, current ignore-count 0

It is an area border and autonomous system boundary router

In the following example, the following output appears when the show ip ospf command has been entered during the time when the router is in the ignore state: 

Router# show ip ospf 1


Routing Process "ospf 1" with ID 192.168.0.1

Supports only single TOS(TOS0) routes

Supports opaque LSA

Supports Link-local Signaling (LLS)

Supports area transit capability

Maximum number of non self-generated LSA allowed 14000

   Threshold for warning message 75%

   Ignore-time 5 minutes, reset-time 10 minutes

   Ignore-count allowed 5, current ignore-count 1

   Ignoring all neighbors due to max-lsa limit, time remaining: 00:04:52

It is an area border and autonomous system boundary router

The following output appears when the show ip ospf command has been entered after the router left the ignore state: 

Router# show ip ospf 1


Routing Process "ospf 1" with ID 192.168.0.1

Supports only single TOS(TOS0) routes

Supports opaque LSA

Supports Link-local Signaling (LLS)

Supports area transit capability

Maximum number of non self-generated LSA allowed 14000

   Threshold for warning message 75%

   Ignore-time 5 minutes, reset-time 10 minutes

   Ignore-count allowed 5, current ignore-count 1 - time remaining: 00:09:51

It is an area border and autonomous system boundary router

The following output appears when the show ip ospf command has been entered for a router that is permanently in the ignore state: 

Router# show ip ospf 1


Routing Process "ospf 1" with ID 192.168.0.1

Supports only single TOS(TOS0) routes

Supports opaque LSA

Supports Link-local Signaling (LLS)

Supports area transit capability

Maximum number of non self-generated LSA allowed 14000

   Threshold for warning message 75%

   Ignore-time 5 minutes, reset-time 10 minutes

   Ignore-count allowed 5, current ignore-count 6

   Permanently ignoring all neighbors due to max-lsa limit

It is an area border and autonomous system boundary router

Additional References

The following sections provide references related to the OSPF Link-State Database Overload Protection feature.

Related Documents

Related Topic
Document Title

Configuring OSPF

•Cisco IOS IP Routing Protocols Configuration Guide


Standards

Standards
Title

None

—


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

None

—


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.

•max-lsa

Glossary

LSDB—link-state database.

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