When designing the routing for an Enterprise Campus network it is important to keep which of the following route filtering aspects in mind?

Route filtering provides independent value by controlling which prefixes are advertised or accepted; it does not require summarization to be useful, and the two techniques complement rather than depend on each other.

Filtering outbound updates at the Enterprise Edge so that only the default route and aggregate summary prefixes are advertised to remote sites prevents detailed internal subnet information from leaking externally, reduces the routing table size on remote routers, and avoids topology exposure - while still providing full reachability through the summaries and default route.

IGPs such as EIGRP and OSPF propagate all learned routes throughout the routing domain by default and have no built-in mechanism to block inappropriate transit traffic; explicit route filtering or policy is required.

Route filtering can be applied on both inbound and outbound updates on Cisco routers; restricting it to outbound only is factually incorrect and would leave the design unable to control what routing information is accepted.