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.

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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

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 OSPF Link-State Database Overload Protection

Limiting 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 OSPF Link-State Database Overload Protection

Example Setting a Limit for LSA Generation

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

  • "Configuring OSPF" module

Standards

Standards

Title

None

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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

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Technical Assistance

Description

Link

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Glossary

LSDB --link-state database.