OSPF Summarization Restrictions Within an Area

OSPF is a link-state routing protocol that relies on all routers within an area maintaining an identical link-state database (LSDB). This requirement is fundamental to the protocol's operation and ensures accurate shortest path calculations. As a result, OSPF does not allow route summarization within an area. Summarization or filtering of LSAs or routes within an area would lead to inconsistencies in the LSDB across routers, potentially causing incorrect routing decisions. This restriction helps maintain the integrity of the OSPF routing process and ensures that all routers have a complete and accurate view of the network topology within their area.

A workaround that will yield desired results is to use distribute list filtering which allows you to filter routes from entering the Routing Table.

Links:

https://forum.networklessons.com/t/how-to-configure-ospf-summarization/923/92?u=lagapidis

https://networklessons.com/ospf/how-to-configure-ospf-summarization

https://networklessons.com/ospf/ospf-distribute-list-filtering