IP Source Guard: The Ultimate Defense Against Spoofed IPs

Introduction: The Physical Lockdown

DHCP Snooping stops fake servers, but what stops an employee from manually changing their laptop's IP address to pretend they are the CEO? This is a classic 'IP Spoofing' attack on a local network. The solution is the third piece of the modern LAN security triad: IP Source Guard.

The Binding Table

IP Source Guard relies on the database created by DHCP Snooping. The network switch knows that the computer plugged into Port 12 legitimately negotiated the IP `10.0.0.50`. If the computer on Port 12 starts trying to send data using the 'Source IP' of `10.0.0.1` (the router or the CEO), the switch blocks the data instantly.

Conclusion

IP Source Guard ties an IP address physically to the port on the wall. It makes identity theft on a local network mathematically impossible. See your local binding table here.