DHCPsnoopingin

DHCP snooping is a Layer 2 security feature implemented on network switches. It operates by distinguishing between trusted and untrusted DHCP interfaces. A trusted interface is typically connected to a legitimate DHCP server or another switch that is also participating in DHCP snooping. Untrusted interfaces are those connected to end-user devices.

The primary function of DHCP snooping is to prevent malicious or misconfigured devices from acting as DHCP servers. Attackers can exploit vulnerabilities in the DHCP protocol by setting up rogue DHCP servers. These rogue servers can then hand out incorrect IP addresses, default gateway information, or DNS server addresses to clients, leading to denial-of-service attacks or man-in-the-middle attacks.

DHCP snooping works by intercepting DHCP messages. It builds and maintains a binding table that maps IP addresses, MAC addresses, lease times, and VLAN/interface information for clients that have received a valid IP address from a trusted DHCP server. When a DHCP message arrives on an untrusted port, the switch examines it. If the message appears to be from a rogue server, such as a DHCP OFFER or ACK message arriving on an untrusted port, the switch will drop the packet.

This mechanism helps ensure that only authorized DHCP servers can assign IP addresses to clients on the network. It is a crucial component of network security, particularly in enterprise environments, and is often used in conjunction with other security features like Dynamic ARP Inspection (DAI) and IP Source Guard.