Lets say that we have a topology where A and B are ABR's and send Type 3 LSA's to router C that is OSPF adjacent to them on Area 1.
So, the topology is roughly like this:
Now lets talk about just A and C.
Should area range command on A be used to summarize:
a. Type 3 LSA's advertised by the ABR A to C in another area
b. Not all Type 3 LSA's but only Routes installed by C that point to A as next hop. In other words, if both A and B are each advertising 10 Type 3 LSA's to C, and C installs only 5 of them pointing to A as next hop, then should A summarize on these 5 routes only or on all the 10 Type 3 LSA's?
Thanks a lot
The behavior of area range on ABR A will depend on which area are you summarizing.
If you perform an area 0 range, ABR A will summarize routes from Area 0 into Area 1 - per your example.
If you perform an area 1 range, ABR A will summarize routes from Area 1 into Area 0 - per your example.
Both conditions are irrevelant to the advertising router shown in the RIB as both ABRs have the same OSPF database.