RFC 1247 mandated that area border routers attached to stub areas must summarize all inter-area routes into the stub areas. However, while area border routers connected to OSPF stub areas must originate default summary links into the stub area, they need not summarize other routes into the stub area. The amount of summarization done into stub areas can instead be put under configuration control. The network administrator can then make the trade-off between optimal routing and database size.
This change appears in Sections 12.4.3 and 12.4.4.