This configuration filters the received LSAs, and only those matching the filtering conditions are
involved in the Shortest Path First (SPF) calculation to generate the corresponding routes. It does not
affect the link status database or the route table of the neighbors. It only affects the routing entries
calculated by local OSPF. This function is used to control routes that enter the ABR or ASBR.
The following route-map rules will be supported if the route-map parameter is configured:
match interface
match ip address
match ip address prefix-list
match ip next-hop
match ip next-hop prefix-list
match metric
match route-type
match tag
Filtering routes by using the distribute-list in command affects forwarding of local routes, but does
not affect route computation based on LSAs. Therefore, if route filtering is configured on the ABR,
Type 3 LSAs will still be generated and advertised to other areas because routes can still be
computed based on LSAs. As a result, black-hole routes are generated. In this case, you can run the
area filter-list or area range (containing the not-advertise parameter) command on the ABR to
prevent generation of black-hole routes.
The following example configures LSA filtering.
Ruijie(config)# access-list3permit172.16.0.00.0.127.255
Ruijie(config)# router ospf 25
Ruijie(config-router)# distribute-list 3 in ethernet 0/1
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