IP Source Guard and DHCP Snooping

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 IP address of the legitimate host.

IP Source Guard uses dynamic DHCP snooping and static IP source binding to match IP addresses to hosts on untrusted Layer 2 access ports. At first, 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 s static IP source binding is configured, 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 uses the DHCP snooping binding database to permit or deny incoming IP traffic. The binding database entry provides a valid source IP address, MAC address, and VLAN information on interface, which IP Source Guard uses to install a TCAM rule in the device.