5.2.a Implement and troubleshoot switch security features

5.2.a [iv] IP source-guard

IP source guard provides source IP address filtering on a Layer 2 port to prevent a malicious host from impersonating a legitimate host by assuming the legitimate host’s IP address. The feature uses dynamic DHCP snooping and static IP source binding to match IP addresses to hosts on untrusted Layer 2 access ports.

Initially, all IP traffic on the protected port is blocked except for DHCP packets. After a client receives an IP address from the DHCP server, or after static IP source binding is configured by the administrator, all traffic with that IP source address is permitted from that client. Traffic from other hosts is denied. This filtering limits a host’s ability to attack the network by claiming a neighbor host’s IP address . IP source guard is a port-based feature that automatically creates an implicit port access control list (PACL).

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 5214-5217).  . Kindle Edition.

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SY/configuration/guide/ip_source_guard.html