3Com Router 3000 Ethernet FamilyConfiguration Guide Chapter 4 OSPF Configuration3Com Corporation4-18Note:z The filter-policy import command only filters the OSPF routes of this processreceived from the neighbors, and routes that cannot pass the filter are not to beadded to the routing table. This command only takes effect on ASBRs.z The filter-policy export command takes effect only on the routes redistributedusing the import-route command. If you do not configure the import-routecommand to redistribute external routes (including OSPF routes of differentprocesses), then the configured filter-policy export command does not take effect.This is because OSPF advertises routing information by sending LSAs rather thanrouting tables.z If no routing protocol is specified, the filter-policy export command applies to allredistributed routes specified using the import-route command.4.2.11 Configuring Route Aggregation by OSPFI. Configuring the Route Aggregation of OSPF AreaRoute aggregation means that ABR can aggregate information of the routes of thesame prefix and advertise only one route to other areas. An area can be configuredwith multiple aggregate segments, thereby OSPF can summarize them. When the ABRtransmits routing information to other areas, it will generate Sum_net_Lsa (type-3 LSA)per network. If some continuous segments exist in this area, you can use theabr-summary command to summarize these segments into one segment. In this way,ABR only sends an LSA after aggregation. No LSA that falls into the specifiedaggregation network segment of this command will be separately transmitted. TheLSDB scale in other areas is accordingly reduced.Once the aggregate segment of a certain network is added to the area, all the internalroutes of the IP addresses in the range of the aggregate segment will no longer beseparately broadcast to other areas. If the keyword not-advertise is used to qualify thenetwork segment, the summary route information to the network segment will not bebroadcast. This network segment is defined by IP address/mask.Note: Only when configured on ABR can route aggregation take effect.Perform the following configuration in OSPF area view.
