This chapter covered basic information about installing and configuring Cisco IDS sensors. You learned about choosing a placement for a sensor and how to determine whether to place the sensor in front of the firewall or behind the firewall (or perhaps in both locations). The chapter also described the different models of sensors Cisco currently offersfrom the little IDS-4215 at 80Mbps to the massive IDS-4250-XL that can support 1000Mbps. The chapter also discussed IDS modules, which are another option for networks. You also learned the necessary upgrade preparations that you must make prior to upgrading sensor models from pre-IDS 4.0 to 4.0. Finally, the chapter described and demonstrated the initial setup of the sensor and the creation of a service account.