Open Shortest Path First (OSPF) supports a user-defined maximum number of prefixes (routes) that are allowed to be redistributed into OSPF from other protocols or other OSPF processes. Such a limit could help prevent the router from being flooded by too many redistributed routes.
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may not support all the features documented in this module. For the latest
caveats and feature information, see
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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 table.
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Prerequisites for OSPF Limit on Number of Redistributed Routes
It is presumed that you have OSPF configured in your network, along with another protocol or another OSPF process you are redistributing.
Information About OSPF Limit
on Number of Redistributed Routes
If large number of IP
routes are sent into OSPF by redistributing Border Gateway Protocol (BGP) into
OSPF, the network can be severely flooded. Limiting the number of redistributed
routes prevents this potential problem.
OSPF can receive and accept packets from non-routable addresses (for
example, 0.0.0.0/7) also.
How to Configure OSPF Limit the Number of OSPF Redistributed Routes
This section contains the following procedures, which are mutually exclusive. That is, you cannot both limit redistributed prefixes and also choose to be warned.
This task describes how to limit the number of OSPF redistributed routes. If the number of redistributed routes reaches the maximum value configured, no more routes will be redistributed.
The redistribution limit applies to all IP redistributed prefixes, including summarized ones. The redistribution limit does not apply to default routes or prefixes that are generated as a result of Type-7 to Type-5 translation.
Example OSPF Limit on Number of Redistributed Routes
This example sets a maximum of 1200 prefixes that can be redistributed into OSPF process 1. Prior to reaching the limit, when the number of prefixes redistributed reaches 80 percent of 1200 (960 prefixes), a warning message is logged. Another warning is logged when the limit is reached and no more routes are redistributed.
Example Requesting a Warning About the Number of Redistributed Routes
This example allows two warning messages to be logged, the first if the number of prefixes redistributed reaches 85 percent of 600 (510 prefixes), and the second if the number of redistributed routes reaches 600. However, the number of redistributed routes is not limited.
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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Feature Information for OSPF Limit on Number of Redistributed Routes
The following table
provides release information about the feature or features described in this
module. This table lists only the software release that introduced support for
a given feature in a given software release train. Unless noted otherwise,
subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform
support and Cisco software image support. To access Cisco Feature Navigator, go
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Table 1 Feature Information for OSPF Limit on Number of Redistributed Routes
OSPF supports a user-defined maximum number of prefixes (routes) that are allowed to be redistributed into OSPF from other protocols or other OSPF processes. Such a limit could help prevent the router from being flooded by too many redistributed routes.
The following commands are introduced or modified in the feature documented in this module: