The Cisco Firewall Services Module (FWSM) is an integrated firewall module for high-end Cisco Catalyst 6500 switches and Cisco 7600 series routers used by large enterprises and service providers. You can install up to four FWSMs in a single switch chassis. Cisco FWSM is based on Cisco PIX firewall technology, and offers unmatched security, reliability, and performance.
Firewall Best Practices