ip ospf database-filter all out or under router ospf 1 : neighbor 1.1.1.1 database-filter all out --- "Rizkalla, Simon" <srizkalla@uecomm.com.au> wrote:

Does anyone have any idea how to filter out LSA updates between areas? I am using the Cisco 7204 VXR routers as ABRs and Enterasys routers as ASBRs. However, I do not want routes to be propagated from the backbone area to any other area. The limitation is that the Enterasys gear we are using does not support NSSAs.

Regards,

Simon Rizkalla

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Hi Simon, I have some experience in this area that might help. By default, OSPF floods new LSAs out all interfaces in the same area, except the interface on which the LSA arrives. OSPF will flood based on the characteristics we discussed earlier in this chapter, I am mentioning this because OSPFs specific behavior is continue flooding until an acknowledgement on the Link State Update packet is received. Some redundancy is desirable, because it ensures robust flooding and accurate routing. However, too much redundancy can waste bandwidth and might destabilize the network due to excessive link and CPU usage in certain topologies. For example the bandwidth consumed by OSPF in a fully meshed topology could be considerable and it might them be desirable to block flooding. You can block OSPF flooding of LSAs two ways, depending on the type of networks: 1. On broadcast, nonbroadcast, and point-to-point networks, you can block flooding over specified OSPF interfaces. 2. On point-to-multipoint networks, you can block flooding to a specified neighbor. On broadcast, nonbroadcast, and point-to-point networks, to prevent flooding of OSPF LSAs out of a specific interface, use the following command in interface configuration mode: ospf database-filter all out On point-to-multipoint networks, to prevent flooding of OSPF LSAs to a specific neighbor, use the following command in router configuration mode: neighbor ip-address database-filter all out Hopefully this maybe of assistance to you, good luck! Tom Thomas -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of Rizkalla, Simon Sent: Monday, December 10, 2001 7:30 PM To: nanog@merit.edu Subject: OSPF LSA filtering Does anyone have any idea how to filter out LSA updates between areas? I am using the Cisco 7204 VXR routers as ABRs and Enterasys routers as ASBRs. However, I do not want routes to be propagated from the backbone area to any other area. The limitation is that the Enterasys gear we are using does not support NSSAs. Regards, Simon Rizkalla