Lab 24: OSPF Multiple Area Routing, Authentication, Path Manipulation, Default Routing-Part II

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OSPF Flooding Reduction

OSPF flooding reduction was introduced in Cisco IOS Software Release 12.1(2)T. Inherently, OSPF LSAs are refreshed every 3600 seconds. In large, fairly stable OSPF networks, this can lead to large amounts of unnecessary LSA flooding from area to area. Technically, if an LSA has not changed, why reflood it every 3600 seconds? OSPF flooding control is a new technique that changes normal LSAs into DoNotAge LSAs. Therefore, they will not get flooded every 3600 seconds across areas. For this feature to work, all routers in the area that are connected to the router performing flooding control must be running Cisco IOS Software Release 12.1(2)T or later. To enable flooding control on the interface, use the following interface command:

 Router(config-if)#  ip ospf flood-reduction  

Additionally, you can choose to block all LSA flooding out an interface. To block OSPF flooding of LSAs on broadcast, nonbroadcast, and point-to-point interfaces, use this following interface command:

 Router(config-if)#  ospf database-filter all out  

To block LSAs flooding to a specific neighbor, use the following router command on the neighbor statement:

 Router(config-router)#  neighbor   ip_address   database-filter all out  
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CCIE Practical Studies, Volume I
CCIE Practical Studies, Volume I
ISBN: 1587200023
EAN: 2147483647
Year: 2001
Pages: 283
Authors: Karl Solie

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