What devices should not be part of a network’s perimeter defense?

None of the above

Th e security perimeter is the fi rst line of protection between trusted and untrusted networks. In general, it includes a fi rewall and router that helps fi lter traffi c. Security perimeters may also include proxies and devices, such as an intrusion detection system (IDS), to warn of suspicious traffi c. Th e defensive perimeter extends out from these fi rst protective devices, to include proactive defense such as boundary routers which can provide early warning of upstream attacks and threat activities. Page 765.