OSPF is link state routing protocol that works on the concept of areas. All areas must have same LSDB (link state database); hence OSPF summarization can only done on the border routers i.e. on ABR (Area border router) and ASBR (Autonomous system bou...
http://www.ebrahma.com/2013/10/route-summarization-in-ospf/Labels: ABR, advertise, ASBR, not-advertise, OSPF-is-link-state-routing-protoco, Route-Summarization-in-OSPF, Summary-route, Summary-route-calculation