IS-IS and OSPF areas

Question

What is the main difference between the kinds of routes permitted by default into IS-IS and OSPF areas?

Answer 1

By default, each and every route is advertised into all OSPF regions. This comprises inter area OSPF and external routes which have been injected into the OSPF. By default, IS-IS doesn’t advertise inter area or external routes into a region, however injects a default route.