When configuring DHCP snooping, follow these guidelines:
* DHCP snooping is not active until you enable the feature on at least one VLAN, and enable DHCP globally on the switch.
* Before globally enabling DHCP snooping on the switch, make sure that the devices acting as the DHCP server and the DHCP relay agent are configured and enabled.
* If a Layer 2 LAN port is connected to a DHCP server, configure the port as trusted by entering the “ip dhcp snooping trust” interface configuration command.
* If a Layer 2 LAN port is connected to a DHCP client, configure the port as untrusted by entering the no ip dhcp snooping trust interface configuration command.