OSPF DB Protection

You can use OSPF database protection to limit the number of link-state advertisements (LSAs) generated by the local router in a given OSPF routing instance, thus preventing the link-state database from being flooded with excessive LSAs. This feature is particularly useful if you have configured VPN routing and forwarding on the provider edge (PE) and customer edge (CE) routers, using OSPF as the routing protocol. An overrun link-state database on the CE router can exhaust resources on the PE router and impact the rest of the service provider network. When OSPF database protection is enabled, the maximum number of LSAs specified includes all LSAs whose advertising router ID is not equal to the local router ID (non-self-generated LSAs). These might include external LSAs as well as LSAs with any scope such as the link, area, and autonomous system (AS). When the specified maximum LSA count is exceeded, the database typically enters the ignore state. In this state, all neighbors are brought down, and non-self-generated LSAs are destroyed. In addition, the database sends out hellos but ignores all received packets. As a result, the database does not form any full neighbors, and therefore does not learn about new LSAs. However, if the warning-only option is configured, only a warning is issued, and the database does not enter the ignore state but continues to operate as before.